2.1. The synergetic relation of the interpretative principles

It is perhaps the most common scenario in the case law that the Court invokes and applies the comparative interpretation, the dynamic interpretation, the principle of effectiveness, and the interpretation in light of PIL norms together. The synergetic application of these principlesFootnote ¹¹ leads to the expansion of the applicability and scope ratione materiae of the rights and freedoms under the ECHRFootnote ¹² or to the incorporation of positive obligations under the protective scope of the ECHR.Footnote ¹³ In such instances, the need to ensure effective and practical guarantees and the dynamic interpretation harmoniously coexist with and are best served by reading the ECHR in light of other PIL norms. The European consensus, namely the comparative interpretation on the basis of the law and practice of member states, overlaps with the interpretative impact inferred by PIL norms.

However, even when these four interpretative principles reinforce the same interpretative result, the distinctive function of the principle of taking other PIL norms into account is still evident. The synergetic relationship between the interpretative principles is not fixed, but may evolve subject to the use and the weight accorded to the external PIL norms. A pertinent example is the Court's case law on whether the right to consultation falls within the applicability of Article 11 of the ECHR. The Court, in its early judgments, had employed provisions of the European Social Charter (ESC)Footnote ¹⁴ and the International Labour Organization (ILO) Conventions No. 87Footnote ¹⁵ and No. 98Footnote ¹⁶ as well as their expert bodies’ views as an a contrario argument in order to exclude the right to consultation from the applicability of Article 11 of the ECHR.Footnote ¹⁷ On these occasions, relevant PIL norms were used as a means to limit the expansive interpretation of the ECHR.Footnote ¹⁸ Yet, in the Demir and Baykara and Wilson, National Union of Journalists cases the same PIL norms reinforced and supplemented the Court's legal reasoning in the opposite direction. The Court acknowledged that the collective agreement in question constituted an integral part of the applicants’ freedom of association but only in light of the specific factual circumstances.Footnote ¹⁹ The interpretative impact of these relevant PIL norms (the interpretation of which had also been developed by the European Social Charter's Committee of Independent Experts) to the construction of Article 11 of the ECHR was further evolved by the Grand Chamber in its judgment in the Demir and Baykara case: the consideration of PIL norms became an autonomous and sufficient legal justification for enlarging as a matter of law the applicability of Article 11 of the ECHR.Footnote ²⁰ In all these cases, the Court cumulatively invoked the principle of effectiveness, the dynamic interpretation, and the interpretation by taking PIL norms into account, but it was the greater weight attached to PIL norms that led to a different interpretation of Article 11 of the ECHR and the overruling of the previous case law.

There are many similar instances in the Court's jurisprudence when the principle of interpreting the ECHR in light of these norms was the driving force behind the adoption of radically different interpretations of the ECHR.Footnote ²¹ The fact that external PIL norms are frequently dispositive of the cases before the CourtFootnote ²² lends support to the argument that the use of PIL norms does not only confirm – but also establishes – the content of the ECHR.Footnote ²³

2.2. Distinguishing the interpretative principle of taking other PIL norms into account from the comparative (or consensual) interpretation

The Court's practice of taking PIL norms into account is often approached as an integral part of comparative or consensual interpretation.Footnote ²⁴ The idea of European consensus is seminal to the Court's reasoning in so far as their reliance upon PIL norms is concerned. In the Demir and Baykara case the Grand Chamber proclaimed (and have since reiterated) that the interpretation of the ECHR by taking PIL norms into account is based on the existence of a European consensus, namely the common international and/or domestic law standards accepted by the vast majority of states.Footnote ²⁵

The identification (or the construction) of a perceived consensus frequently involves the conflation of member states’ practice with PIL norms. Even when member states’ national legislation and practice converge with international standards, the Court should still treat them as distinct sources of law and enquire into their reasoning.Footnote ²⁶ That said, the idea of the European consensus (as originally construed by the Court and commonly referred to in the literature) falls short of explaining the Court's actual practice.Footnote ²⁷

It is not atypical for the Court to rely on PIL norms in the absence of common legal standards in national practice;Footnote ²⁸ or, all the more, when member states present contrary national practices.Footnote ²⁹ The Court, by virtue of interpreting the ECHR in light of PIL, also pervades areas in which states traditionally enjoyed a great margin of appreciation – the sphere of imposing criminal sanctions;Footnote ³⁰ the protection of the environment;Footnote ³¹ or the immigration context,Footnote ³² for example. Hence, PIL norms have been disassociated and are independent from national practice. The external norms do not serve a role supplementary to the comparative interpretation, in establishing or strengthening the existence of national practice, but yet their impact to the interpretation process is decisive.

It is also clear that, despite the absence of discernable consensus, the Court still uses external PIL norms. The Court employs treaties in its judgments to demonstrate the existence of commonly accepted standards, even if said treaties are not ratified and accepted by the majority of statesFootnote ³³ or are not yet in force.Footnote ³⁴ It seems that the ordinary meaning of the requirement of being accepted by the vast majority of states is not strictly followed. The Court also disregards the absence of consensus among states, as clearly reflected in certain treaties. In the D.H. and Oršuš cases, even though the Framework Convention for the Protection of National Minorities (FCNM)Footnote ³⁵ prescribed programme-type provisions evidencing the explicit lack of agreement among states, the Court interpreted the ECHR in light of the provisions of the FCNM and the progressive views of its Advisory Committee.Footnote ³⁶

Furthermore, the practice of taking PIL norms into consideration is distinct from the comparative interpretation and its European consensus underpinnings, since the Court employs PIL norms which are not evidence of a European consensus. PIL norms have a determinative impact on the Court's reasoning, without being European developments or confirming the existence of a common regional perspective.Footnote ³⁷ Examples include other regional treaties on human rights (such as the Inter-American Convention on Human Rights),Footnote ³⁸ specialized regional treaties (for example, the Inter-American Convention on the prevention, punishment, and eradication of violence against women),Footnote ³⁹ or universal treaties (such as the ICC StatuteFootnote ⁴⁰ or the International Covenant on Civil and Political Rights taken together with the views of the Human Rights Committee).Footnote ⁴¹ In these cases, the European nexus is weak, if it exists at all.Footnote ⁴²

Consequently, the Court uses the European consensus as a rhetorical tool to legitimize the use of PIL in its judgments. The invoked consensus legitimizes progress,Footnote ⁴³ even in cases where the Court admits it is consensus in formation.Footnote ⁴⁴ This line of justification gives the false impression of a positivistic perception of the existence of common European standards, which are to be found and not created by the Court.Footnote ⁴⁵ This is why the Court is inclined towards the European consensus idea and construing its reasoning on the alleged consensus among member states.Footnote ⁴⁶ Yet, it is clear that the interpretative practice of taking other PIL norms into account functions autonomously to the comparative or consensual interpretation.

2.3. Distinguishing the interpretative principle of taking other PIL norms into account from the dynamic interpretation

The principle of interpreting the ECHR by taking PIL norms into account is also distinct from the dynamic (or evolutive) interpretation, namely the construction of the ECHR in light of the changing legal landscape of the member states’ practice.Footnote ⁴⁷ The reason that the former is analytically subordinated to the latter is due to the substantial overlap between the two principles: PIL norms are included in the legal developments in light of which the ECHR must be read.Footnote ⁴⁸ The Court regularly invokes dynamic interpretation and interpretation of the ECHR in light of other PIL norms in a synergetic fashion (cumulatively) to enlarge the applicability of the rights under the Convention, including the recognition of the retroactivity of the more favourable criminal law under Article 7 of the ECHR;Footnote ⁴⁹ the recognition of indirect discrimination under Article 14 of the ECHR;Footnote ⁵⁰ the acknowledgment of the right to collective bargaining and the right to consultation under Article 11 of the ECHR;Footnote ⁵¹ and the inclusion of human trafficking in Article 4 of the ECHR.Footnote ⁵²

The two interpretative principles differ, however. First, the evolutive interpretation is substantiated by reference to sources of law other than PIL, such as national law, or non-legal developments. Second, the consideration of PIL norms may function as a limitation to the application of the dynamic interpretation.Footnote ⁵³ This is the case when PIL norms are considered insufficient so as to pursue and ground a dynamic interpretation of the Convention due to lack of consensus among member states.Footnote ⁵⁴ Third, the principle of taking PIL norms into account does not share a fundamental characteristic of the evolutive interpretation. It is generally accepted – and there is nothing in the Court's jurisprudence to suggest otherwise – that the changing conditions in the member states’ practice could not justify reducing the protective scope of rights under the ECHR.Footnote ⁵⁵ Consequently, evolutive interpretation always follows the higher standards, thereby expanding the scope of the ECHR. In contrast, as will be discussed below, interpretation by taking PIL norms into account may restrict the scope of rights. Hence, the two principles of interpretation may lead to different interpretative outcomes as far as the construction of the ECHR is concerned.

2.4. Distinguishing the interpretative principle of taking other PIL norms into account from the principle of effectiveness

The principle of effectiveness attains a cardinal place in the Court's jurisprudence, prescribing that the rights and freedoms under the ECHR must be accorded their full weight and effect. Even though this principle usually converges with the principle of taking PIL norms into account, the two interpretation principles can also be in tension and should, therefore, be treated separately.Footnote ⁵⁶

This is the case when the Court takes cognizance of PIL norms, which restrict the protective scope of the rights under the ECHR. The Court recalls that, while being mindful of the special character of the ECHR as a human rights treaty, it should not be placed in a vacuum. On the basis of Article 31(3)(c) VCLT,Footnote ⁵⁷ the ECHR must be interpreted by taking other relevant rules of international law into account and in harmony with these rules (as far as possible). This was the legal reasoning in the well-known Al-Adsani caseFootnote ⁵⁸ and the same approach has been followed in subsequent case law concerning the international customary rules on stateFootnote ⁵⁹ and diplomatic immunity.Footnote ⁶⁰ Similarly, the Court regularly takes other treaty provisions into account, which counter the principle of guaranteeing effective and practical rights under the Convention.Footnote ⁶¹

Of particular interest is the fact that the Court hides the tension between the principle of effectiveness and the principle of taking cognizance of PIL norms. The reference to the guarantee of practical and effective rights is made, at best, in passing in these judgments; the Court instead stresses the necessity of not applying the ECHR in a vacuum.Footnote ⁶² Conversely, in instances where the relevant PIL norms reinforce the effective protection of the rights and freedoms under the ECHR the Court fully elaborates on the necessity of applying the principle of effectiveness.

The tension between the two principles reveals the different interests that they purport to serve in the Court's reasoning. On the one hand, the principle of effectiveness preserves the specificity of the ECHR and stresses its ‘self-contained’ function in order to ensure the most practical and effective rights possible. This is an ‘isolationist’ approach in so far as the relationship of the ECHR vis-à-vis other PIL norms is concerned. On the other hand, taking PIL norms into account may restrict the scope of rights and freedoms, but ensures that the ECHR is read consistently, to the extent possible, to other relevant PIL norms. The fact that the ECtHR acknowledges the relevance of the external rules to the construction of the ECHR and attaches considerable weight to them suggests that it highly values (and perhaps occasionally prioritizes) the need to read the ECHR by taking cognizance of PIL norms, even if this approach results in the pursuit of an interpretation that would (drastically) restrict the scope of the rights under the ECHR.

To conclude, the foregoing analysis illustrated that the Court employs the principle of interpreting the ECHR by taking other PIL norms into account in an independent fashion without subordinating it to the other seminal principles of interpretation in its case law. The conceptualization of its interpretative practice in this way resolves many ambiguities in its legal reasoning and brings the dynamic interrelation of different principles of interpretation into the fore. The systematization of the said interpretative practice into an autonomous principle of interpretation reinforces the suggestion that the ECtHR not only is mindful of embedding the ECHR within PIL but also considers itself to have the duty to construe the ECHR in light of other PIL norms.

3.1. Fragmentation by default? The contextual differences between the external PIL norms that the Court uses and the ECHR

A fundamental aspect of the fragmentation of international law is that similar or even identical norms attain different meanings and interpretations, in light of the structure, aim, and specificities of a given treaty.Footnote ⁶⁴ Despite a core of similarity in equivalent treaty provisions, there is a core of difference as well.Footnote ⁶⁵ Hence, the decision-maker must give due regard to the different treaty context from which the external PIL norm originates.

The ECtHR acknowledges the contextual nuances of external PIL norms and draws the appropriate interpretative inferences from these norms. Examples include whether the purposive element of the definition of torture in Convention Against Torture (CAT)Footnote ⁶⁶ should be transposed in Article 3 of the ECHR, since the CAT has a different structure and purpose to a treaty protecting human rights;Footnote ⁶⁷ the relevance of the definition of rape under international criminal law to the ECHR;Footnote ⁶⁸ or the contextual nuances between, on the one hand, the ILO ‘labour law’ and the ESC ‘industrial relations’ paradigms and, on the other hand, the ECHR which is first and foremost a civil and political rights treaty.Footnote ⁶⁹ There are instances, however, in which apparent differences in context, as clearly reflected in the text of other relevant treaty provisions, have been disregarded or downplayed.Footnote ⁷⁰ The contextual differences of PIL norms that appear to be similar or even identical highlight the inherent limitations underpinning the role of the interpreter in mitigating fragmentation. Variances in the practices and/or case law of international bodies and courts accordingly should be treated as a reflection of the different aims and values served by the respective treaties.Footnote ⁷¹ At the same time, the unity of PIL is to be preserved, unless context dictates otherwise.Footnote ⁷²

An integral part of the different treaty context of the employed external PIL norms is their progressive development by their (if existent) respective monitoring bodies. The ECtHR is careful to read the relevant PIL norms by taking cognizance of their interpretation by their supervisory bodies. In this sense, the provisions of the ICCPR and the Convention on the Elimination of All Forms of Discrimination Against WomenFootnote ⁷³ are read in light of their supervisory bodies’ views in individual communications;Footnote ⁷⁴ the ILO Conventions are placed against the background of the views of the ILO Committee of Experts, the recommendations of the ILO Committee on Freedom of Association, and the ILO Committee on Freedom of Association.Footnote ⁷⁵ The practice of placing the external treaty provisions in their own dynamic environment eradicates the possible scenario of two international bodies interpreting the same PIL norm in different ways. The Court relies upon and uses a provision of an external treaty in line with its development through time by its supervisory body. This practice enhances consistency and harmonization of standards in PIL while different international bodies progressively develop them.

The VCLT principles of interpretation (Articles 31–33) do not appear to explicitly address the interpretative evolution of treaties by their supervisory bodies,Footnote ⁷⁶ although one could argue that their practice may qualify as a subsequent practice in the application of the treaty under Article 31(3)(b) of the VCLT.Footnote ⁷⁷ This is a point that should be kept in mind regarding the possible limits to adopting the VCLT as the sole framework for effectively mitigating the difficulties arising from the fragmentation of PIL. International courts and tribunals may develop innovative interpretative practices.

In the event that an international treaty does not have a supervisory body, the ECtHR is usually willing to consider its interpretation by other international courts and bodies. In the Neulinger and Shuruk case the Court looked into the case law of supreme courts of member states to the Hague Abduction Convention in order to identify the meaning of serious risk in Article 13(b) of the said Convention.Footnote ⁷⁸ In Al-Jedda the Court sought for the interpretation of Article 103 UN CharterFootnote ⁷⁹ in the ICJ Advisory Opinion in the Namibia case.Footnote ⁸⁰ Yet, in Al-Skeini the Court did not take into consideration the extensive international practice on the concept of jurisdiction despite the detailed written submission by the third-party interveners.Footnote ⁸¹

Even though the practice of the Court to identify how an external PIL norm is construed by another international body is to be welcomed, it brings new interpretative difficulties to the fore. When the ECtHR takes external treaty provisions into consideration, it inevitably engages with the interpretation of these provisions (in order to ascertain their ordinary meaning, at least). In this way, the Court exercises interpretative authority over this ‘foreign’ norm, especially if its interpretation is contested.Footnote ⁸² Moreover, the Court's engagement with the interpretation of an external norm further increases the likelihood of diverging interpretations by different international (and national) bodies and, hence, deepens fragmentation. In the X and others case before the Grand Chamber seven judges dissented to the majority's judgment in so far as their interpretation and use of the European Convention on the Adoption of Children was concerned.Footnote ⁸³ They opined that the Court's interpretation did not adhere neither to the letter nor the object and purpose of Article 7 of the said Convention.Footnote ⁸⁴ Therefore, unless caution is exercised, an international court's receptiveness to other PIL norms and, hence, its universalistic approach, may, in certain instances, give rise to further fragmentation difficulties.

3.2. The concept of ‘relevant’ PIL norms

In its jurisprudence the Court systematically refers to the relevant PIL norms that it must take into consideration when interpreting the ECHR. Nonetheless, it does not elaborate on which are the relevant norms. The International Law Commission did not provide any guidance in its Fragmentation Report when it discussed the notion of ‘relevant rules’ under Article 31(3)(c) VCLT.Footnote ⁸⁵ Academic literature rarely addresses the question and, when it does, it adopts rather circular approaches.Footnote ⁸⁶ The determination of which are the relevant PIL norms is an important matter because it relates to the predictability of the legal reasoning and the interest of legal certainty in the Court's methodology. Moreover, the consideration of relevant norms may lead to radically different interpretations of the ECHR and, therefore, it could potentially involve unequal treatment of similar cases before the Court.

To give an example, in the Siliadin and Rantsev cases the Court employed two different readings of Article 4 of the ECHR in light of different relevant PIL norms respectively, although both cases concerned victims of human trafficking. In Siliadin the Court focused on the alleged violation of the prohibition of slavery under Article 4 of the ECHR. It ascertained the ordinary meaning of the term ‘slavery’ by employing the definition of slavery as encapsulated in Article 1(1) of the 1926 Slavery Convention.Footnote ⁸⁷ The human trafficking aspect of the case was completely ignored by the Court, even though the applicant's arguments involved such claims.Footnote ⁸⁸ In contrast, the Court in Rantsev took one step forward and enlarged the applicability of Article 4 by recognizing human trafficking within its scope. By broadening the array of relevant norms, it added another layer of PIL norms to be taken into account for the interpretation of Article 4 of the ECHR, relying heavily on the UN Palermo Protocol to Prevent, Suppress and Punish Trafficking in Persons, especially Women and ChildrenFootnote ⁸⁹ and the Anti-Trafficking Convention.Footnote ⁹⁰ On this basis, the Court read detailed obligations into the protective scope of Article 4 (and Article 2) of the ECHR and assessed the respondent states’ acts and omissions against the yardstick of the obligations under the Palermo Protocol and the Anti-Trafficking Convention.Footnote ⁹¹ The Siliadin and Rantsev cases exemplify that different relevant PIL norms may not only have a substantially differing impact on the interpretation of the ECHR, but that they may also result in selectivity, treating individual applications unequally and imposing different positive obligations on the respondent states.Footnote ⁹² The jurisprudence of the Court witnesses other similar instances as well.Footnote ⁹³ It is for this reason that the meaning of the relevant rules needs closer attention.

Generally, the concept of relevance is looser than the notion of the ‘same subject-matter’ as envisaged in Article 30 of the VCLT,Footnote ⁹⁴ but one should not lose sight that relevant rules are those which provide aid for and inform the interpretation of a specific treaty provision rather than those applying in a situation generally.Footnote ⁹⁵ In other words, a meaningful relationship must be established between the external norm and the treaty under interpretation. Former President of the ICJ, Dame Rosalyn Higgins, stressed this point in her Separate Opinion in the Oil Platforms case.Footnote ⁹⁶ She found that the majority's reasoning was insufficient to justify the consideration of the totality of substantive international law on the use of force for interpreting a provision of a US-Iranian treaty concerned with economic and commercial issues (a friendship, commerce, and navigation treaty). She noted that, according to Article 31(3)(c) of the VCLT, certain rules are relevant if, and to the extent that, they are sufficiently related to the context of the treaty under interpretation. Higgins specifically argued that the ‘type of the treaty’Footnote ⁹⁷ should be an important criterion. The criterion, however, for ascertaining the type of treaty under interpretation is not very clear or straightforward in cases other than contrasting a commercial and economic treaty to the corpus of PIL on the use of force. Moreover, this criterion appears to attach the meaning of relevant rules closer to the same subject matter requirement of Article 30 of the VCLT and, thus, restricts the notion of relevant rules.

On the other hand, there is merit in the idea that the concept of relevance includes a greater spectrum of PIL norms, without being necessarily embedded within or directly related to the context of a treaty. Article 31(3)(c) of the VCLT does not mention that relevant PIL rules should be part of the context of a treaty, but that they will be taken into account together with the context.Footnote ⁹⁸ The ICJ in the Questions of Mutual Assistance case favoured this approach when it accepted France's argument that the 1977 Treaty of Friendship and Co-operation between France and Djibouti was relevant for interpreting the 1986 Convention on Mutual Assistance in Criminal Matters.Footnote ⁹⁹ The ICJ, by way of applying Article 31(3)(c) of the VCLT, affirmed that the 1977 Treaty had a ‘certain bearing’Footnote ¹⁰⁰ on the interpretation of the 1986 Convention, although no substantial link connected the two treaties (the fields of co-operation envisaged in the 1977 Treaty did not include judicial co-operation as prescribed under the 1986 Convention). The certain bearing of the 1977 Treaty on the interpretation of the 1986 Convention indicates that if a PIL norm is of limited relevance to the treaty provision under interpretation, then the interpretive impact should be also limited. The higher the degree of abstraction, the lower the impact on the interpretation of the treaty in dispute.Footnote ¹⁰¹ Likewise, the closer to the so-called context of a treaty under interpretation another PIL norm is, the greater bearing and interpretative impact may the latter advance on the former. The relevance-impact dependence seems appealing. It suggests a model inclusive of varying degrees of relevant norms by virtue of establishing a meaningful relationship between the external norm and the treaty provision under interpretation.Footnote ¹⁰²

The practice of the ECtHR is inclined towards this model. In its reasoning the Court gives regard to and uses PIL norms that are not directly related to the context of the ECHR (accepting that the ECHR is a treaty on the protection of human rights, mostly civil and political rights).Footnote ¹⁰³ Pertinent examples are bilateral or plurilateral treaties settling matters arising from war or occupation,Footnote ¹⁰⁴ or the European Convention on Mutual Assistance in Criminal Matters.Footnote ¹⁰⁵ If a more restricted approach to the concept of relevance were to be adopted, it is doubtful that these PIL norms would qualify as relevant for the interpretation of the ECHR. The fact that the ECtHR interprets the ECHR by taking a great variety of relevant PIL norms into account, suggests, in principle, that the Court employs a policy of embedding the ECHR into PIL and, hence, avoids taking any isolationist or fragmented approaches towards PIL.

Nonetheless, the model of the varying degrees of relevant PIL norms, as appealing and inclusive as it may be, still needs to address a series of questions. Establishing a meaningful relationship between an ECHR provision and an external PIL norm presupposes that the Court must determine the degree of relevance of the external norm to the ECHR. How relevant the PIL norm is for the purposes of interpreting the ECHR is directly linked to appreciating the different treaty context from which the external PIL norms originates, as was discussed in the previous subsection. The degree of relevance of the said external norm also determines the interpretative weight that should be attached to the external norm when interpreting the ECHR.Footnote ¹⁰⁶ The impact of an external norm to the construction of a given right under the ECHR was precisely the object of the preliminary objection ratione materiae submitted by Moldova before the Grand Chamber in the Tănase case. Moldova strongly argued that the Court should not have used the European Convention on NationalityFootnote ¹⁰⁷ in order to construe the ECHR and that the weight attached to said Convention was not appropriate.Footnote ¹⁰⁸ The Grand Chamber dismissed the objection by proclaiming that ‘[i]t is for the Court to decide which international instruments and reports it considers relevant and how much weight to attribute to them’Footnote ¹⁰⁹ without further elaboration. Turkey was similarly concerned in Demir and Baykara, arguing that ILO Conventions were not relevant in the context of Article 11 of the ECHR and that the Court cannot create new rights under the ECHR by way of interpretation.Footnote ¹¹⁰ Further, the United Kingdom in the National Union of Rail, Maritime and Transport Workers case opposed the interpretative relevance of the legal assessments of the European Committee on Social Rights and the ILO Committee of Experts to the construction of Article 11 of the ECHR to include the right to secondary industrial action.Footnote ¹¹¹ Although the Court extensively used these legal assessments, it openly addressed – for the first time – the respondent state's concerns and acknowledged that other international bodies do indeed have different standpoints when discussing their own constitutive instruments.Footnote ¹¹²

The growing concerns raised by the member states amply demonstrate the need for transparent legal reasoning and foreseeability in the case law. Although it is upon the Court to ascertain questions of relevance and weight afforded to external PIL norms, it is also obliged to provide reasons for its judgments – especially when departing from its previous jurisprudence.Footnote ¹¹³ The interpretative exercise of establishing and clearly explaining the meaningful relationship between the ECHR provision under interpretation and the external PIL norm can be challenging. This exercise mirrors the delicate balance between, on the one hand, placing the ECHR against the background of other PIL norms and, on the other hand, recognizing that the contextual differences of other treaties should set a limit to their impact on the ECHR.

3.3. The concept of PIL norms ‘applicable in the relations between the parties’

Article 31(3)(c) of the VCLT explicitly prescribes the requirement that any relevant rules of international law that will be taken into account for the interpretation of a treaty must be applicable in the relations between the parties. It is currently contested whether the parties under Article 31(3)(c) are only the parties to a given dispute or all contacting parties to the treaty under interpretation.Footnote ¹¹⁴

The ECtHR seems to adopt an altogether different position regarding the meaning of applicable rules. In its analysis it refers to treaties ‘applicable in the particular sphere’Footnote ¹¹⁵ or ‘applicable in respect of the precise subject matter of the case concerned’.Footnote ¹¹⁶ The term applicable appears, therefore, attached to the subject matter of the case (commonly referred to in the case law as the international law background to the legal questions before it), rather than to the condition that the rule has to be applicable in the relations between the parties.Footnote ¹¹⁷ The Grand Chamber explicitly dismissed Turkey's preliminary objection in the Demir and Baykara case, according to which the relevant PIL norms should be applicable between the parties and, hence, binding on the respondent state.Footnote ¹¹⁸ The Court does not hesitate to employ treaties that are neither binding on all member states to the ECHR nor binding on the respondent state.Footnote ¹¹⁹

The fact that the Court does not consider itself bound by the requirement that the external PIL norm has to be applicable in the relations between the parties is further reinforced by the regular use of non-binding law (soft law) for interpreting the ECHR. Pertinent examples of non-binding materials include the Council of Europe Parliamentary Assembly resolutions;Footnote ¹²⁰ the Universal Declaration on Human Rights;Footnote ¹²¹ and reports by UN Special Rapporteurs.Footnote ¹²² The Court does not draw a clear line between the sources of law and non-binding materials. This introduces uncertainty to its legal reasoning and unpredictability as to the precise obligations of the member states.Footnote ¹²³ On the other hand, this flexible approach leaves space for creative thinking, especially when the Court discerns evolving trends on the regional and international level.Footnote ¹²⁴ The use of soft law should not be excluded at the outset, as long as the Court is cautious with, first, the choice of documents it employs and, second, their interpretative impact on the construction of the ECHR.

The consideration of soft law in interpreting a treaty is a question that has not been effectively addressed either by the ILC's work on fragmentation or in academic literature. Soft law may aid the interpretation of a treaty provision as evidence of its ordinary meaning.Footnote ¹²⁵ It could be also argued that non-binding norms have normative and evidentiary value when informing the interpretation of a treaty.Footnote ¹²⁶ The IACtHR stands on the other side of the spectrum, by not only acknowledging the evidential weight of soft law in discerning the ordinary meaning of the IACHR, but also by using soft law to establish the content of the rights under the IACHR.Footnote ¹²⁷ More specifically, as far as Article 31(3)(c) of the VCLT is concerned its applicability could be triggered, if it is to be accepted that ‘rules of international law’ include non-binding sources of law. The prevalent view at the moment is that Article 31(3)(c) of the VCLT does not come into play in the case of considerations that are not firmly established as binding rules,Footnote ¹²⁸ although it has been carefully noted that the current practice of international courts is insufficiently developed.Footnote ¹²⁹

3.4. The role of Article 31 (3)(c) VCLT in the jurisprudence of the Court

Despite the reference of Article 31(3)(c) of the VCLT in certain high profile and controversial cases before the European Court, the Court's case law does not often refer to the provision.Footnote ¹³⁰ Although the Court has an extensive practice of taking cognizance of PIL norms, it is clear that it does not share the ILC's and international scholars’ enthusiasm for the use of Article 31(3)(c) of the VCLT.Footnote ¹³¹

Some scholars support the view that the Court applies the provision in an implicit or indirect way.Footnote ¹³² However, such an argument does not seem plausible. First, the assumption that the Court implicitly applies Article 31(3)(c) of the VCLT is a hypothetical exercise and, in any event, there is no reason that the Court would not explicitly invoke and apply the provision, if it were deemed necessary. Second, there is a current trend in literature to invoke Article 31(3)(c) of the VCLT for every instance that a treaty is interpreted in light of other PIL norms, whereas there are also other interpretative principles envisaged in Article 31 of the VCLT that are well placed to accommodate and justify the use of PIL norms as a means of interpretation.Footnote ¹³³ Third, and most importantly, the Court's methodology when taking other PIL norms into account clearly does not meet the requirements of Article 31(3)(c) of the VCLT since it feels at ease with taking cognizance of general principles of law,Footnote ¹³⁴ non-binding norms and treaties neither applicable in the relations between the parties nor binding on the respondent state. Furthermore, in certain of the few instances that the Court invoked Article 31(3)(c) of the VCLT, the text of the judgments strongly indicates that Article 31(3)(c) serves the role of an inspirational and rhetorical reference (the provision is placed in brackets and is mentioned with pertinent cases).Footnote ¹³⁵

The crucial question is, however, whether the non-application of Article 31(3)(c) qualifies as a shortcoming in the Court's practice. In the view of the present author, the answer is in the negative. As far as customary international law and general principles of law are concerned, the non-use of Article 31(3)(c) of the VCLT does not seem to be material. The duty to interpret a treaty by taking customary international law and general principles of law into account forms part of the common sense of the international judge, without necessarily requiring the application of Article 31(3)(c) of the VCLT.Footnote ¹³⁶

Turning now to the use of other PIL norms, besides international custom and general principles, it must be stressed that Article 31(3)(c) of the VCLT poses complicated problems regarding its own interpretation.Footnote ¹³⁷ International courts and tribunals have different approaches on the meaning of ‘relevant’ and rules ‘applicable in the relations between the parties’. This adds merit to the view that, when international courts and tribunals apply the same interpretative principle, they do it in different ways, due to their own specificities and the flexibility of the VCLT interpretative principles.Footnote ¹³⁸ Therefore, even if the ECtHR applied the provision, there would be substantial leeway for its own interpretation of the provision. Finally, one could argue that since the Court has an established practice of taking PIL norms into account, the challenges of the fragmentation of PIL are effectively mitigated regardless of whether Article 31(3)(c) is used.

These points do not imply that international courts and tribunals, including the ECtHR, should not apply the VCLT principles of interpretation. The VCLT framework enhances the adoption of common (to the extent possible) interpretative practices and of a unified vocabulary for addressing fragmentation and preserving the unity of international law.Footnote ¹³⁹ However, one should not a priori exclude other interpretative approaches, which may not follow Articles 31–33 of the VCLT to the letter. Such approaches can potentially be added in future as legitimate understandings of Articles 31–33 of the VCTL.Footnote ¹⁴⁰ Moreover, despite its flexibility, the VCLT is not exhaustive. By way of example, the VCLT interpretative principles do not appear to accommodate the dynamic development of treaties by their supervisory bodies, which is a significant facet of the fragmentation of international law. The ECtHR, however, accommodates this phenomenon in its practice. A different approach would fall short of grasping the evolving interpretation of PIL norms by different international bodies and the need to harmonize varying perceptions to the extent possible.