I. Positivism and Custom

A law-making body might turn a custom into a law. And a community's respect for a custom might be such that the custom operates like a law. But could a custom ever be law without it having been made so? If a custom could be law in its own right, a court which decided according to that custom would not be making law but applying law which already existed. Only someone who believes in fairy tales would have it that there exists a body of hidden but perpetual customary law awaiting judicial detection, Lord Reid observed in 1972, and nobody believes in fairy tales any longer.Footnote ¹ Yet around that very time no less a figure than Friedrich Hayek was insisting that the tale was true: “law existed for ages before it occurred to man that he could make or alter it”,Footnote ² and “those formulating the rules do no more … than to find and express already existing rules, a task in which fallible human beings will often go wrong, but in the performance of which they have no free choice”.Footnote ³ This article considers how Hayek's core assertion – that a rule need not be made as law in order for it to be a legal rule – is distinctively affirmed in the history of English law.

Hayek rejected “the positivist doctrine stand[ing] … in flagrant conflict with what we know about the history of our law”.Footnote ⁴ Laws are coercive orders, the classical positivists argued, whereas customs are not. Customs can be turned into laws – a legislature might do this expressly (by enactment) or “obliquely”Footnote ⁵ (by not abrogating and therefore tacitly assenting to a court's decision to “impress [a custom] with the character of law”Footnote ⁶ ) – but “[c]ustom of itself maketh no law”.Footnote ⁷ A custom which has not been made into law “is nothing more than a rule of positive morality” – something “generally observed by the citizens … but deriving … force … from the general disapprobation falling on those who transgress it”.Footnote ⁸ The custom might be a source of legitimate expectations for its beneficiaries, and might be treated by those burdened by it as a reason for acting in a particular way, but it is only a law if it has been made law.Footnote ⁹ There is no innately legal custom awaiting judicial discovery.

Like many others since, Hayek thought that anyone intent on grasping what eluded the classical positivists did well to reach for H.L.A. Hart's The Concept of Law.Footnote ¹⁰ Whereas classical positivists insisted that a custom only becomes a law when a legislature enacts a rule legalising it or a court applies it to a dispute, Hart set out an argument supporting the conclusion that a custom can be a law in its own right. Statutes do not become law only once judicially interpreted, Hart insisted, for, if they did, a person today found liable for breach of a statutory duty never previously interpreted by a court could reasonably object that she broke no law when she acted; a court's first application of a statutory rule would always take effect retroactively. Might not the same reasoning be applied, he asked, to custom as a source of law? “Why, if statutes made in certain defined ways are law before they are applied by the courts in particular cases, should not customs of certain kinds also be so?”Footnote ¹¹ To answer that the statute, “before it is applied by a court, … has already been ‘ordered’” whereas “a custom has not” is but to assert “the dogma” that only orders ascribable to a sovereign or his subordinates can rank as law.Footnote ¹² It is equally unsatisfactory to answer that a legislature's not having abrogated a court's decision enforcing a custom shows it tacitly to approve of that decision, for it is conceivable that the legislature dislikes a decision but leaves it undisturbed because it has bigger battles to fight, say, or because it does not want to be seen as meddlesome.Footnote ¹³ Yet how can a custom be law, just as a statute is a law, before a court has ever pronounced on it? Because the criteria by which legal officials identify what counts as law within a particular legal system – the criteria which form the content of its “rule of recognition” – make it possible for officials to speak of customs of certain kinds as valid laws. A criterion of validity might be, for example, that a custom is to be identified as a rule of the legal system if is established as “long customary practice”Footnote ¹⁴ and if no statute or other legal source prevents legal officials from relying on this criterion to identify the custom as a legal rule.

It is by no means obvious that Hart prevailed over the classical positivists on the topic of customary law. These “customs of certain kinds” cannot be law simply by virtue of having long been practised without disturbance, Austin had observed, for there are “customs immemorially current in the nation” which “are not legally binding”, just as some customs which are legally binding “had no existence till times comparatively recent”.Footnote ¹⁵ The claim that a custom has the status of law sui generis by virtue of some characteristic – its longevity, its popularity, its reasonableness or whatever – is unconvincing if customs can have this status yet lack the characteristic, or if they can have the characteristic without ever being, or needing to be, recognised as law. There must be some test of recognition by which legal officials can identify customary laws (as distinct from spontaneous customs and legalised customs). Hart drew no conclusions as to what the test might be.Footnote ¹⁶

Could a legal system embody such a test? Hart's reflections on the legal status of custom (“not in the modern world a very important ‘source’ of law”Footnote ¹⁷ ) were understandably sketchy, for the topic was not prominent on his agenda when he rejected classical positivism and made his case for a fresh start. The cursoriness of the reflections should not mask their significance, however, for they have some basis in English legal history. Particularly before the emergence of stare decisis, judges and lawyers regularly sought to explain how some customs had the status of law even though no law-maker or court had ever invested those customs with legal validity. There is to be discovered in this history no single comprehensive test for ascertaining a custom's inherent legal validity – though the identification of a custom as law often involved the proposition that it had endured since time immemorial – and the courts, which would sometimes enforce a custom even though it did not satisfy any accepted test, were hardly immune to the classical positivists’ charge that they impressed customs with the character of law. But the lack of a clear-cut test, and the fact that judges would sometimes legalise customs, does not negate the possibility of a legal system's ultimate rule of recognition embodying some criterion or criteria of validity enabling the courts to identify custom as a distinct source of law. Pre-stare decisis English judges and lawyers, we will see, would typically identify a custom as innately legal – as distinct from a custom which either was not law or had been made law – by virtue of its conformity to a standard of legal validity which was itself customary in nature.

This article is not a disquisition on the general topic of law and custom. Rather, it considers how, historically, English lawyers have tended to understand and explain custom as a source of law in its own right. English legal history does not so much flesh out Hart's own laconic observations on custom as a source of law as lend credence to a general Hartian perspective on the topic. If a criterion of validity by which legal officials identify a custom as law is posited rather than customary – as would be the case, for example, with a statute providing that a customary practice establishes a legal right if it has endured substantially unaltered for the past 40 years – the custom which meets with the criterion is not customary law but custom made binding by positive law. A custom which is customary law has this status because the criterion of validity enabling its identification as law is itself customary. Note how this last proposition trades on two distinct conceptions of custom: a municipal court which identifies a community custom (what Bentham called custom in pays) as law is invoking a standard of legal validity which is customary in the sense of its being a custom of the courts and the legal profession (Bentham's custom in foro).Footnote ¹⁸ So long as a legal system's ultimate rule of recognition allows for customs in foro as part of its content, it will be possible for judges and lawyers to identify a community custom as law (before it has been applied as law) on the basis that the custom conforms to a standard of validity which is identifiable as customary law of the courts.Footnote ¹⁹ But what customary standard, or standards, of validity might courts ever invoke to identify community custom as already existing law?

Prescription is the standard of validity most often applied by English courts to identify a custom as binding law. Although prescription is nowadays commonly thought of as legislated rather than judicial doctrine,Footnote ²⁰ the notion that a custom is law because it has prescribed is one which was accepted and refined in the courts and in legal writings. The history of the doctrine, even distilled, is messy. It yields no definitive explanation of prescription as a test of custom as law (not least because there is, we will see, more than one conception of custom as law), and although custom deemed already law is invariably taken to be prescribed custom, there were differences of opinion among pre-stare decisis English lawyers as to whether or not custom could be declared law solely on the basis of its having prescribed.Footnote ²¹ The history confirms, nevertheless, that a feature of the rule of recognition within a municipal legal system may be that its courts identify some community customs as legally binding by relying on criteria of validity which (notwithstanding possible legal disagreements over their specifics) themselves exist as custom in foro.

II. Customary Law and Common Law

Precedent and statute are the main sources of English law. But it was not always thus. Precedent emerges late in the history of the common law – it would take until the nineteenth century for the courts to become properly equipped to develop the common law according to the principle that like cases should be treated alike.Footnote ²² Before then, a case (or line of cases) would typically be treated as persuasive rather than as binding authority – as something which judges might recognise as venerable legal opinion, and which a lawyer might rely on in court because it provided evidence of what the common law was rather than because it was itself common law.Footnote ²³

The common law itself was a form of custom – though this observation cannot stand unqualified. A custom is a pattern of behaviour identifiable in a community. We do not, as individuals, have our own customs (we have habits), but we do share customs with others. Behaviour according to a custom is not compelled but rather, assuming the custom not to be in decline or obsolete, is expected – what the community considers the done thing rather than merely what it does. There is, of course, a difference between an aggrieved party complaining about my failure to do the done thing and her claiming that my failure to do the done thing was a breach of legal duty. Could my departure from custom amount to breaking the law?

Medieval courts answered that it could – that customs could bind as customary law. But it is important, for at least two reasons, to exercise caution with the concept of customary law. First, the popular depiction of customary law as unwritten law is slightly misleading. Although the earliest English legal writers set forth no distinct theory of law or legal origins, they were clear that laws need not be written: “if, merely for lack of writing, they [i.e. unwritten laws] were not deemed to be laws”, the prologue to Glanvill has it, “writing would doubtless supply to written laws a force of apparently stronger authority than either the justice [equitas] of him who decrees them or the reason of him who establishes them”.Footnote ²⁴ It is no great leap from this reasoning to the conclusion that English law is composed of two types of law: “the written law” and “unwritten laws or customs”.Footnote ²⁵ But customary law will usually have been documented in some way or other – in records of court proceedings, for example, or in legal writings. The observation that customary law is unwritten means only that it is not written as law rather than that it must be “merely oral”.Footnote ²⁶

The second, and for our purposes more important, reason for proceeding with caution is that customs which were understood to bind as customary law were not common law. Blackstone described unwritten – un-enacted – law as falling into three categories: “peculiar laws” (Blackstone had in mind rules of civil and canon law) which “have been … received … by … custom in … courts” with jurisdiction to deal with religious, military, admiralty and university matters but which “bind not the subjects of England”Footnote ²⁷ ; “particular customs … which affect only the inhabitants of particular districts”Footnote ²⁸ ; and “general customs, or the common law … by which proceedings and determinations in the king's ordinary courts of justice are guided and directed”.Footnote ²⁹ The distinction between the last two categories is important. Late-medieval and Renaissance English lawyers typically understood binding customs to be not common law but rather customs which held good in a locality – examples would be local customs relating to trade, inheritance, tenure and wardship – as exceptions to the common law. In Anthony Fitzherbert's Abridgement, first published in 1514, the entry for “custom” is devoted entirely to local customs tried before manorial court juries and held enforceable as lex loci in the localities where they prevailed.Footnote ³⁰ A century later John Davies, in his account of the arguments presented before the King's Bench in the Case of Tanistry, observed how “custom, in the intendment of the law, is such usage as has obtained legal force, and is in reality a binding law to such particular place, persons and things which it concerns”.Footnote ³¹ Thomas Hedley said much the same before Parliament in his famous speech of 1610 condemning the king's impositions.Footnote ³² A local custom was a tricky proposition. A court enforcing one was in essence declaring a special law to prevail, in the relevant locality, over the general non-statutory law of the land. Judges would understandably be disinclined to make such a declaration without being confident of what the customs of the locality were, and that the alleged custom really did exist.Footnote ³³

The common law, then, was understood to be customary (derived from general custom), but there was also this other category of law – local customs enforced by local and royal courts so as to be binding within a locality – which was customary law but not common law. A “custom cannot be alleged generally within the kingdom”, Coke insisted in the late 1620s, “for that is the common law”.Footnote ³⁴ With the common law – this was the crux of Coke's point – nothing needed to be alleged as custom: law which was common law was by definition within the knowledge of judges, and so there was no reason for lawyers to mention it in writs or pleadings. The point was clearly on Henry Finch's mind when, writing around the same time, he proclaimed mercantile custom to be general custom – part of the common law rather than something which merchants had to demonstrate; it was “not good” legal technique to “plead that there is a custom among merchants throughout the realm” regarding the recognition of bills of exchange, for “that which is current throughout the realm, is common law, not custom”.Footnote ³⁵ This distinction between common and customary law was not always straightforwardly negotiated,Footnote ³⁶ not least because judges had to be confident that a custom prevailed in every locality throughout the realm if it was to be treated as common law.Footnote ³⁷ Lawyers had nevertheless conceived of the distinction long before the mid-sixteenth century, by which point they were drawing it regularly.Footnote ³⁸

III. Testing Custom

What were the criteria of validity by which a lawyer could identify custom as law? Pre-stare decisis common lawyers were certainly not in perfect agreement on what the criteria were. Nevertheless, it is possible to discern, in English legal literature from the thirteenth through to the seventeenth century, some recurrent insights regarding how a custom might have the force of law without this force having been conferred on it by an appropriate authority. These insights, though they have little direct bearing on legal systems which recognise customary law but which make no pretense to antiquity,Footnote ³⁹ are valuable for anyone intent on understanding customary law in the abstract because they illustrate how the identification of custom as law in its own right depends upon a workable test distinguishing custom which has this status from custom which is merely spontaneous or which has been made into law.

Longevity is sometimes considered to be the relevant test: a custom with the status of law is, on this account, a shared pattern of behaviour converging around a norm which is recognisable as a legal norm because that pattern of behaviour has persisted undisturbed for a long time.Footnote ⁴⁰ Versions of the test have been formulated by various legal anthropologists, and can be found in Roman law and in international law.Footnote ⁴¹ In pre-stare decisis English law, a custom was considered already existing law because the relevant normative pattern of behaviour had prevailed fundamentally unaltered in the community for a long time, which was usually taken to mean that nobody could testify to a time when things were otherwise.Footnote ⁴² Whereas it had to be proved that a local custom had persisted since time beyond memory, the antiquity of a general custom was treated as fact. “[T]he realm has been continuously regulated by the same customs as it is now”, John Fortescue asserted around 1470.Footnote ⁴³ For Coke, writing almost a century-and-a-half later, “the grounds of our common laws … were beyond the memory or register of any beginning”.Footnote ⁴⁴ Both men would have understood the thinking of the fifteenth-century serjeant-at-law who proclaimed that “[c]ommon law has existed since the creation of the world”,Footnote ⁴⁵ even if they might have opted for (slightly) more measured language.Footnote ⁴⁶

It is, of course, one thing to claim that it has always been a custom and another to claim that it has long been a custom. Medieval civilians and canonists could seem very relaxed about the formation of custom (“[w]hen something is done twice”, one thirteenth-century civilian claimed, “this makes a custom”Footnote ⁴⁷ ) and were inclined to treat customs as legally binding after the passing of but a few decades.Footnote ⁴⁸ The concept of “immemorial” custom was not novel to England – canonists would sometimes refer to custom which conflicted with the laws of the church as consuetudo quae excedit hominum memoriam,Footnote ⁴⁹ and the idea of custom transcending memory is to be found in Roman law.Footnote ⁵⁰ But in England after the Norman Conquest, the notion of a custom having existed throughout and beyond human memory came to be understood according to a distinct legal definition.

To settle on a point in history before which nobody currently alive could provide reliable testimony regarding events is to fix a date distinguishing time within from time outside human memory. If enforceable custom must be immemorial, judges and jurors might have their task made easier by a rule which states that legal memory began at a specific time; then, at the very least, any custom which can only have obtained since that time – which, for one or another reason, could not have existed at that time – could be ruled not immemorial and therefore unenforceable. But how, in English law, was time immemorial to be legally defined?

The answer is somewhat complicated. Medieval real actions for the recovery of possession of land (seisin) were subject to limitation by past events. In the late twelfth century, a claimant seeking to recover had to trace a right of seisin from ancestors who had held that right since, but not before, the accession of Henry I (5 August 1100). Around 1200, the reference point for establishing rightful seisin was changed to 1 December 1135 (the day of Henry I's death). The Provisions of Merton 1236 changed the date again to the accession of Henry II (19 December 1154), and the first Statute of Westminster (1275) changed it yet again to the year of the coronation of Richard I (3 September 1189).Footnote ⁵¹

These were statutes, not judge-made law. Moreover, they were limitation statutes rather than rules enacted to legalise customs. But the last of these rules endured a peculiar fate: the limitation date established in the first Statute of Westminster was co-opted as custom in foro. By the early fourteenth century, attorneys and judges were using the date of Richard I's accession to the throne analogously so as to fix the outer limit of the prescription period for the acquisition of easements and other incorporeal hereditaments.Footnote ⁵² Early year book cases quite often concern testimony “from time whereof there is no memory” (du temps dount il ny ad memorie).Footnote ⁵³ Sometimes there is no basis for inferring anything other than that judges were interpreting this phrase literally: as meaning “beyond the memory of anyone still alive”. But sometimes they took the phrase to mean something else: “before the beginning of the reign of Richard I”.Footnote ⁵⁴ Thomas Littleton, writing in the 1450s, remarked on how there was “title of prescription … at the common law before any statute of limitation of writs … where[by] a man will plead a title of prescription by custom. He shall say, that …when … a matter is pleaded … no man then alive hath … knowledge to the contrary”.Footnote ⁵⁵ But there was also, Littleton observed, “a title of prescription” understood according to the statutory limitation on recovery of seisin (which ran “from the time of king Richard the First after the Conquest, as is given by the statute of Westminster the First”), whereby a failed action for recovery was presumed to vest lawful title in the person in possession or enjoyment of land.

Just what it meant to say that a custom had prescribed because it was beyond memory differed depending on whether the custom was local or general. When lawyers and judges referred to an immemorial local custom (or to an incorporeal right having been acquired by virtue of the doctrine of prescription) they originally meant that there was nothing to contradict testimony that the custom (or the enjoyment on which a prescription claim was founded) had continued without interruption since 1189. It seems unlikely that actual evidence of continuous user since this date would have been treated as a prerequisite to ruling that a local custom had prescribed, even in the late-thirteenth century, for providing such evidence was for the most part practically impossible. Certainly there were indications, by around the second half of the fourteenth century, that the strict test was being supplanted by a more relaxed one: juries were ever more regularly instructed to infer the existence of a local custom since 1189 if there was evidence of the custom having continued throughout actual living memory.Footnote ⁵⁶ Whatever interpretation might originally have been put on the test for proving immemorial local custom, and however the test might have altered over time, late-medieval and early-modern lawyers certainly understood that there had to be a test: if a local custom was to prevail, which meant its prevailing in derogation from the common law, its antiquity had to be established and could not be merely asserted.Footnote ⁵⁷ Indeed, it was not only the antiquity of the local custom that had to be pleaded and proved: one had to be able to say what the custom was and show where it prevailed,Footnote ⁵⁸ and a court would have to be satisfied that the maintenance of the custom was not unreasonable.Footnote ⁵⁹

But general customs were treated differently. The common law was regularly described as immemorial general custom,Footnote ⁶⁰ and Blackstone wrote of “a rule of the common law” being proved “by showing that it has always been the custom to observe it”.Footnote ⁶¹ But the antiquity, as with the certainty and the reasonableness, of a general custom did not have to be proved.Footnote ⁶² Rather, its antiquity was accepted unless somehow disproved. Even though English common law to this day treats the coronation of Richard I as the date distinguishing time beyond from time within legal memory, the requirement that there be evidence of continued practice or usage for a distinct period of time was never applied to customs from which the common law itself was derived.

Prescribed local custom conformed to the rule of recognition: a local custom bound as an exception to the common law because a jury thought it possible, from the evidence available to the court, to identify that custom as having governed some state of affairs in some particular locality since time immemorial. Since the antiquity of a general custom did not have to be proved for it to be common law, how was the common law to be identified? The custom that carriers of goods compensate owners for damage incurred in transit might be accepted as general and immemorial, as might the custom that a woman takes a man's surname on marrying him. Why should only one of these customs be recognised as part of the common law? Some customs were immemorial and general yet – Austin, we have seen, was wise to the point – not legally significant. Did not the conformity of a general custom to the requirements of the rule of recognition have to entail more than assuming the custom to have persisted since time beyond memory?

Pre-stare decisis common lawyers seem not to have been exercised by this matter. Hayek observes that the immemorial customs affirmed as common law are ones which “give rise to expectations that guide people's actions” and about which “arbitrators … have to decide”.Footnote ⁶³ These customs answer disputes which litigants bring to the courts, and the fact that the customs answer litigants’ disputes is something the litigants themselves should have been able to ascertain (when a court determines that a custom “ought to have guided their expectations”, it does so “not because anyone had told them before that this was the rule, but because this was the established custom which they ought to have known”Footnote ⁶⁴ ). If a court is presented with a novel legal problem, it might have to declare as common law an immemorial custom which has never before received judicial affirmation or been accorded any legal significance – the late-medieval royal court which had no statute or charter to guide it when determining if a writ should be upheld, for example, would ascertain the parties’ rights and obligations in accordance with long-remembered, long-operative common practices.Footnote ⁶⁵ English common lawyers dwelled not on whether immemorial general customs without any apparent legal significance could be latent common law – the answer, implicit in the declaratory theory of the common law, had to be affirmative – but rather on whether the antiquity of a custom which was legally significant spoke to its quality as well as to its status as law. Fortescue put the point pithily. The king, ruling by hereditary right, had the power to interfere with the immemorial customs of the realm. Yet he showed little inclination to do this. Why? Because the king reasonably inferred, from the fact of these customs having endured, that they were “the best” laws possible; had they not been the best, “some of those kings [from whom he descended] would have changed … or … totally abolished them”.Footnote ⁶⁶

But “best” how? Common lawyers developed two broad, interlocking lines of response. Customs endure, first of all, because they are valued through use – customs not practised fall into desuetude. Matthew Hale wrote of how some pre-Conquest laws, though no longer valid as enacted laws, were nevertheless “now … common law, or the general custom of the realm”, because their value to the nation had, over the centuries, been regularly affirmed in charters and coronation oaths.Footnote ⁶⁷ Seventeenth-century lawyers sometimes characterised the common law as customised law – as long-accepted general custom which was not only valued through use but which had also evolved to complement the predilections of the users. A general custom not only “obtaineth the force of law” by virtue of “being continued without interruption time out of mind”, John Davies claimed, but, unlike enacted law, its “iteration and multiplication” – the fact that “people … use it and practise it again and again” – shows it to be “agreeable to their nature and disposition”.Footnote ⁶⁸

The common lawyer's primary observation was not, however, that the endurance of an immemorial general custom showed that people valued and availed themselves of it. Rather, it was that the custom could thereby be seen to be reasonable: a general custom has the status of common law because it is custom which has continued since time immemorial, and it would not have continued thus if it was somehow contrary to reason. According to Christopher St. German an unreasonable custom was void, and a general custom, even if reasonable (by which he meant that it conformed with the law of nature), could not obtain the force of law by virtue of its reasonableness aloneFootnote ⁶⁹ ; a reasonable general custom, if it was to be enforceable as law and alterable only by Parliament, had to be long accepted by the king and his subjects.Footnote ⁷⁰ While St. German was not alone in associating long-established general custom with universal or natural reason,Footnote ⁷¹ those who came after him were more inclined to connect general custom to a type of reason which they considered distinctive to law. Their argument linked the reasonableness of a custom to its use: a general custom was common law because, for so long as anyone could remember, it had governed an issue over which people would sometimes dispute, and if the custom had not governed that issue reasonably it would have fallen by the wayside long ago. Understanding general custom as law, Coke and others maintained, required long study, observation and experience – the “artificial” perfection of reason.Footnote ⁷² But the better description for general custom itself (as opposed to lawyerly erudition on the subject) was “tried” reason. This idea, though it can be traced at least to the Elizabethan eraFootnote ⁷³ (and though it would in due course be associated with Burkean political thought), was particularly prevalent in the first half of the seventeenth century. Custom, on this view, was tested by “time, … the trier of truth, author of all human wisdom, learning and knowledge”,Footnote ⁷⁴ “proved and approved by continual experience to be good and profitable for the commonwealth”Footnote ⁷⁵ ; if a custom “had been found inconvenient at any time”, it would have “been interrupted, and” so would have “lost the virtue and force of a law”.Footnote ⁷⁶

Not every late-Renaissance English lawyer endorsed this notion of general custom as tried reason,Footnote ⁷⁷ and those who did endorse it were essentially refining the standard argument that the customs of the realm were immemorial and innately reasonable. It was a significant refinement, nevertheless, because it reveals common lawyers not confining their explanation of the status of a general custom as common law to the custom having persisted time out of mind. General custom identified as tried reason was common law because its application was not limited to particular places within the realm, because it was immemorial, and because lawyers and judges understood it – from learning, argument, memory and experience – to be both the reason that people behaved (and expected others to behave) in a particular way and a court's justification for ruling as it did on a dispute.

IV. Reasoning from Prescription

It is bewildering, Austin thought, that people's knowledge of the existence of the common law should depend on “the testimony of the judges”, given that the general customs associated with the common law were ones which “people had observed” over a long time.Footnote ⁷⁸ The bewilderment endures only if one understands judges to be supplying testimony as to the existence of common law rules rather than deciding if the rules apply (just as they have to decide if existing statutory rules apply) to cases before them. More troublesome is the presumption that a general custom was common law because it was identifiable as reason which had been tested and proved good over time. The general customs which judges chose to legalise, Bentham observed, were not necessarily the embodiment of tried reason: the first court to rule any particular mala in se (Bentham gave the example of perjuryFootnote ⁷⁹ ) unlawful would have done so not because the custom of abjuring that action had been tested over time but because the wrongfulness of that action was self-evident. For Austin, the presumption that a general custom declared common law must have persisted since time beyond memory was simply unwarranted, because many such customs (he gave the example of bills of exchange) were very obviously of modern provenance.Footnote ⁸⁰

Bentham and Austin belonged to the era when the association of the common law with general custom was very much in demise and its association with the doctrine of precedent in the ascendancy. Custom was exiting the stage even as it was being ushered off. What was being ushered off was, to recall Lord Reid's description, the performance of a fairy tale – a tale about judges who, on appointment, learned the secret formula which gave them entry to the cave containing the common law's treasure. The treasure awaited their discovery; all the judges had to do, when deciding cases, was correctly identify the treasure – declare what was already there – and put it to use.Footnote ⁸¹ Classical positivists insisted (and the received wisdom is that they were right to insistFootnote ⁸² ) that the tale was far-fetched.

But was it? Certainly the declaratory theory is historically inaccurate if it is reduced to the proposition that judges never develop but only declare the common law. But a better estimation of the theory is perhaps that judges, in deciding on disputes between parties, have a primary responsibility to identify and apply the laws governing those disputes when the parties acted.Footnote ⁸³ A court settling a dispute by reference to (local or general) custom would not be purporting to make that custom into law but rather identifying the custom as the law already in place to be applied to the dispute. If, when the parties acted, the law already in place was the custom – if there was no other law that could be identified as governing the dispute – the court is supposed to apply that law. Should you put your cattle out to graze on my land by virtue of local custom, and a court then penalises me because I build a fence which stops you doing this, I might object that the penalty is unfair because I had no way of knowing, at the time that I built the fence, that my action would incur a negative legal consequence. The penalty certainly would be unfair if, at the time that I acted, there was no identifiable custom directing me away from the action that I took (if, as Hayek put it, there was no custom providing an answer which I should have been able to ascertain). But if such a custom was identifiable, and there was no positive law overriding it, you might claim that the custom protected your action and that the real rule-of-law violation would occur if a court now declined to apply the custom and ruled that my stymieing your action was lawful. The success or failure of your claim that the court has a duty to enforce the custom depends on the custom being identifiable as already existing law.

Though English lawyers had no uniform answer to the question of what makes a custom identifiable as already existing law, their answer typically depended on the idea that custom could prescribe. The notion of prescribed custom can seem confusing, since custom and prescription are distinct concepts in English law. Individuals and juridical persons acquire title or forfeit legal actions by virtue of prescription, whereas the benefits and burdens of prescribed local customs are enjoyed and borne by communities.Footnote ⁸⁴ It is presumed, furthermore, that a right acquired by a person through prescription was the subject of a lawful grant at some point preceding legal memory; all that can be proved is that the mode of user or enjoyment which occasions the prescriptive claim has prevailed openly, without force and without interruption – in other words as if, at some point in the past, the right was lawfully granted. A local custom, by contrast, prescribes not to the benefit of any specific (actual or juridical) person but rather to an amorphous community which, having no legal personality, cannot have rights conferred on it. And so whereas rights acquired by prescription are taken to have originated lawfully, “custom to some place … cannot be by grant”.Footnote ⁸⁵ Yet despite these differences between custom and prescription, lawyers from Bracton's time to Coke's are regularly to be found referring to local custom having prescribed, by which they meant that a custom had the force of law because it had been proved to have endured since time immemorial. The year books provide numerous instances of local customs being enforced because nobody alive could provide testimony contradicting long and continuous user,Footnote ⁸⁶ just as they attest to occasions when local customs were adjudged not to bind because they had not prescribed.Footnote ⁸⁷

General customs, we know, were assumed extant since the coronation of Richard I – their status as immemorial custom was notional rather than proved. Judicial proclamations regarding immemorial general customs could sometimes seem rather eccentric. In 1606, for example, Coke declared digging for saltpetre for the manufacture of gunpowder to be a custom of the realm, even though gunpowder production in Britain did not start until around the mid-fourteenth century.Footnote ⁸⁸ For classical positivists, examples of this type were but demonstrations that the common law had to be judge-made. For the declaratory theorist, by contrast, they are evidence that judges can go awry – that they not only might mangle but (if they are identifying a custom as law for the first time) might even be expected to mangle the secret formula which opens the cave.Footnote ⁸⁹ The judiciary is “sworn to determine” the “customs of the land” correctly, Blackstone argued, but if they do so incorrectly (if they make “determination[s] … evidently contrary to reason”) they do not make law but rather make determinations which are “not law… not the established custom of the realm” – and a future court ruling on an allegation concerning the purported custom has the responsibility to “vindicate” the common law “from misrepresentation”.Footnote ⁹⁰

But how would anyone know if the declarer of immemorial custom had got the formula correct? Many lawyers and others long into the Stuart period were wont to treat as unquestionable the proposition that the custom of the realm was custom time out of mind. Yet efforts to substantiate the proposition tended to yield contentious conclusions – especially notorious in this regard are the various seventeenth-century Whig accounts of how the privileges of the commons (as a co-ordinate third estate with the king and the lords) were established customs which pre-dated and had somehow survived the Conquest.Footnote ⁹¹ Although, by the 1600s, English lawyers would still often reason as if every custom of the realm could be taken to have prevailed at least since the twelfth century, claims that some aspect of the common law truly was immemorial in character would often be based – as is perhaps nowhere more clear than in the prefaces to some of Coke's Reports – on dubious, if not outright ludicrous, interpretations of the relevant history.Footnote ⁹² Thomas Egerton (Lord Ellesmere), one of the ablest lawyers of the Jacobean era, seemed unconvinced by the case for the common law's antiquity even as he sought to advance it. That a local custom should only bind if proved to have endured since 1189 struck him as a preposterous notion.Footnote ⁹³ As for general custom, it seemed obvious to him that some parts of the common law had, by the early seventeenth century, become “obsolete and worn out of use: … judges found them to be unmeete for the time they lived in”.Footnote ⁹⁴ So was it not necessary for judges sometimes to create new common-law rules – rules which could not be said to have existed time out of mind? Egerton baulked: were one to understand this to be my opinion, he insisted, “I would be misunderstood, as though I spoke of making new laws … . I speak only on interpretation of the law in new questions and doubts … . [T]he constitution or form of it, or how, or when it was first begun … ought to be obeyed and reverenced, but not disputed”.Footnote ⁹⁵ The idea of general customs surviving unbroken since antiquity troubled him all the same: “ancient common laws are so much neglected, contemned, and almost grown obsolete and out of use that for the most part we have not the substance but the shadow of the ancient common laws.”Footnote ⁹⁶

Yet it seems no exaggeration to claim that every common lawyer of note between the thirteenth and seventeenth centuries thought the status of general custom as common law had something to do with that custom having endured for a very long time. Even Francis Bacon – who showed no interest in the temporal aspect of the common law and who disparaged “[h]e who holds fast to custom and retains the appearance of antiquity in the face of change”Footnote ⁹⁷ – considered it “reasonable that the laws and basic customs of a kingdom or commonwealth be accepted, as ancient boundaries”, where “no event or change has intervened”.Footnote ⁹⁸ Why did English common lawyers accord such significance to a custom's longevity?

Certainly part of the answer was that the persistence of a custom justified inferences as to its possessing other qualities – its being innately reasonable, valuable to its beneficiaries, an embodiment of the people's wisdom, suited to their dispositions and so on. But longevity was, first and foremost, a standard which custom with the status of law could be said to satisfy: this local (or general) custom was customary (or common) law because it had prescribed – because the custom could be proved (or presumed) to have endured since time immemorial. The common-law doctrine of prescription – prescription as custom in foro – was, and technically still is, a feature of the rule of recognition, a criterion of legal validity enabling a court to identify custom as already existing law.

Identifying prescribed custom as law entails distinguishing customs which are from customs which are not immemorial. Customs which a court considers legally valid are (if general) presumed or (if local) have been proved to extend beyond legal memory. Customs which, within legal memory, have altered substantially or have been abrogated (as both general and local customs could be by statute) cannot be said to have prescribed. It is perhaps instructive to turn briefly to international law to see how prescription cannot be a feature of the rule of recognition if a custom is understood to prescribe by virtue of having coalesced through acceptance over time but without the custom being shown or taken to have endured since a time – a specific date, the point beyond which reliable testimony no longer exists – legally accepted as marking out a prescription period. Article 38(1) of the Statute of the International Court of Justice, the original text of which dates back to 1920, provides (inter alia) that the Court shall apply “international custom, as evidence of a general practice accepted as law”. If an international custom is to apply as law, in other words, there has to be a practice which States have freely concurred in or converged on, and those States must also believe (the so-called opinio iuris requirement) that this practice is legally binding. While “it seems difficult to accept” that “prescription is part of treaty law”Footnote ⁹⁹ if the applicability of international custom depends on evidence that a general practice which States accept as law has existed undisturbed since a time beyond legal memory, Verykios argues, prescription is a feature of treaty law if customs need not be immemorial in order to prescribe: so long as we “carefully distinguish … immemorial prescription” from the “actual prescription” (prescription proprement dite) of international custom,Footnote ¹⁰⁰ we might conclude that “prescription is … a general legal principle as part of international law under art. 38”.Footnote ¹⁰¹

For Verykios, the “actual” prescribing of an international custom occurs through its maturation over time.Footnote ¹⁰² Justice Gray famously endorsed this idea in The Paquete Habana: “[b]y an ancient usage among civilized nations, beginning centuries ago, and gradually ripening into a rule of international law, coast fishing vessels … have been recognized as exempt … from capture as prize of war.”Footnote ¹⁰³ Actual prescription deems it irrelevant when a custom ripened into law. The crucial question is whether the custom's state of ripeness can be determined “at the moment the appreciation is being made” by the court issuing a ruling.Footnote ¹⁰⁴ “[I]t is not often that we need to know at precisely what moment the fruit became ripe: we are more interested in knowing, when we bite it, if it is now ripe or still too hard or sour.”Footnote ¹⁰⁵ The analogy is question begging. A court does not make a determination for its own purpose but rather resolves a dispute between party A, who believes that a custom is ripe, and party B, who believes the opposite. For the court to rule in favour of either side on the basis of its “appreciation” of the custom's ripeness leaves the losing side with no explanation as to why its belief that the custom had (or had not) ripened into law was incorrect.Footnote ¹⁰⁶ If the court is not simply to take a side but rather to apply a custom as law (or decline to apply it because it is not law), it must rely on a standard distinguishing customary law from mere custom. Immemorial prescription is such a standard. “Actual” prescription is not.

If a custom is a rule of a legal system, it must conform to the requirements of the rule of recognition: there has to be some test of legal validity enabling legal officials to distinguish that custom from custom simpliciter. Immemorial prescription is not the only conceivable standard. In international law, for example, the standard is more likely to be formulated in terms of a practice being shared rather than having endured: solving and avoiding interaction and co-ordination problems in the international community requires clarity (to take the example from The Paquete Habana) on whether fishing vessels are exempt from capture as prize of war; many States might agree that it is inappropriate to capture these vessels and might believe that they have a legal obligation not to do so; and the agreement among and belief shared by these States might be sufficiently widespread to warrant the judgment that there is a rule of customary international law forbidding the capture of fishing vessels. For the custom on exemption from capture to function as a rule of customary international law, however, these States will have to concur on, among other things, what constitutes sufficiently widespread (as well as sufficiently long-standing) agreement on the inappropriateness of capture, and the extent to which States – and indeed, which States – must believe that their navies are under a duty not to treat fishing vessels as prize of war.Footnote ¹⁰⁷ As with prescription, so too with convergence: it cannot be part of the rule of recognition if the identification of custom as law is deemed possible by subjective assessment, without the need to satisfy the requirements of some standard of legal validity.

V. Conclusion

English lawyers in the centuries separating Bracton and Coke understood (even if they might not have articulated the proposition) that if a custom was to be declared already law, there had to be some criterion or criteria of validity enabling a court to identify that custom thus. To state that prescription was the recognised criterion perhaps simplifies matters inordinately. What it meant to say that a custom had prescribed did not remain unaltered from one context to the next, and claims as to a custom's antiquity sometimes seemed to be but pretexts for other claims (regarding custom as the embodiment of tried reason, for example, or as suited to a community's dispositions). Prescription was, nevertheless, regularly invoked by judges and lawyers to explain how customs could have the force of law without having been legalised by the judiciary or Parliament, and how the court which treated such a custom as dispositive when ruling on a dispute could be said to be enforcing law which already existed rather than turning a custom into law and applying that law retrospectively.

Classical positivists offered a searching critique of this position – a critique which only the rash would dismiss outright. But this does not mean that we do well to join those positivists in concluding that custom which is law could only ever be custom turned into law. When declaring a custom to be law, judges were affirming that the custom satisfied a standard of legal validity which existed as custom in foro. A community custom which had prescribed was considered to satisfy a test identifiable not as a judge-made or statutory rule – though the classic formulation of the test was derived from a limitation statute – but rather as the judiciary's and the legal profession's broad and somewhat fluid understanding of what immemorial custom was (and, when the community was a locality rather than the realm, how custom was to be proved). No doubt judges would sometimes manipulate the test, declaring custom to be law when in fact they were turning it into such – or were instructing jurors in such a way that it ended up turned into such. But it would be a mistake to think that, in reasoning from prescription, judges could never genuinely have been declaring and enforcing custom as law in its own right, according to their responsibility to decide cases by applying the law as it governed the disputants’ rights and obligations when the facts prompting the dispute occurred.