The excommunication of Elizabeth i has reached the level of historical notoriety where it crops up on popular timelines of the period. In early 1570 Pope Pius v issued the bull Regnans in excelsis, which declared Elizabeth i a heretic and freed her subjects from allegiance to her, while simultaneously threatening them with similar punishment if they obeyed her in particular matters. General historical consensus has always been that the bull was greeted by Catholics with an embarrassed downward glance and shuffling of feet, while the English government – and particularly hot Protestants – seized on it with glee as a stick with which to beat recalcitrant papists whenever they fancied a bit of sport.

Somewhat surprisingly, Aislinn Muller's book is the first to be dedicated solely to the excommunication, and in it she seeks to complicate the received wisdom. For her, the pope intended the bull to confer legitimacy on rebellion in England and Ireland, both in the eyes of those on the ground but also key players amongst the Catholic European powers. Equally, Muller judges the bull an attempt to influence European politics more widely, such as ongoing issues in the Low Countries and France in the wake of the Protestant Reformation. Domestically, Muller views the bull as hardening Protestant minds on the succession issue, particularly against Mary, Queen of Scots, while it also helped to confessionalise Elizabethan foreign policy. Rather than just limiting herself to the original bull, Muller also considers subsequent re-visits and judges the one in 1580, around the time of the proposed Anjou match, rebellion in Ireland and the launch of the Jesuit mission to England, to have had far greater impact. As such, the book seeks to view the excommunication from all angles, examining both Catholic and Protestant responses to it between 1570 and 1603.

The opening chapter is perhaps the most effective at shifting perceptions. While historians have frequently – and not incorrectly – linked the bull to the Northern Rebellion of 1569, Muller shows Catholic debates about excommunicating the queen started early in the decade. She shows that France was keen to do it as quickly as possible because of their support for Mary, Queen of Scots. In contrast, Spain was initially more tentative, wary of French designs but its attention also occupied elsewhere, especially towards the Ottoman threat. Indeed, the excommunication was even discussed at the Council of Trent following a request from English exiles in Louvain.

Yet when the excommunication did arrive, it was open to multiple interpretations of what Catholics could and should do. Nevertheless, Muller interestingly shows how copies of the bull were not just prepared for an English audience, but were circulated around Europe. Of course, in England, John Felton ensured that bureaucratic procedure was followed and went for the traditional option, hammering a copy to the door of the bishop of London's palace, for which he was subsequently executed. Taking aim at some admittedly older works of scholarship that dismissed popular knowledge of the excommunication, Muller argues that many people knew about the bull and openly discussed it, meaning that it was central to violent and non-violent resistance to the regime.

The next chapter looks at Protestant responses and provides further evidence that people engaged with the bull's content. For Muller, the irony is that these rejoinders actually did more to publicise the bull than Catholic efforts. Though some polemical responses made predictable mileage out of the word ‘bull’, Muller argues that the fact they did respond shows knowledge of the excommunication, plus official concern about it. In the following chapter, she explores this argument further, suggesting that the excommunication influenced debates about the succession, as it brought in confessional matters rather than just the hereditary principle.

Turning back to Catholic reaction in her final chapter, Muller argues that far from a muted English Catholic response to the bull, it actually provoked resistance, but scholars have been mistaken in thinking that subversion must always be violent. Instead, she somewhat controversially points to seditious speech, the circulation of devotional objects and increased recusancy as ways in which Catholics fulfilled the obligations that the bull set upon them. In contrast, she argues that the bull played a vital role in prompting violent resistance to the colonial English enterprise in Ireland.

Certainly, Muller convinces of the bull's importance and that it deserves more attention than the curt dismissal given by some – but not all – historians. Perhaps more questionable is whether it really was the root cause, or foundation stone, of all that is argued in the book. A factor amongst others, yes, but, for example, that the authorities recorded more devotional objects in circulation after 1571 does not necessarily mean that the bull caused this but that they were looking for such things with increased vigilance. Yes, the bull probably was one of the reasons for this, but what about the founding of the English College at Douai in 1568 or the start of the English Mission in 1574, amongst other contextualising factors?

This also indicates another potential pitfall: sources and how they are treated. For example, a good deal of the sources consulted here are produced by or for the state, including spy reports that need to be approached with extreme caution. An allegation does not mean that something actually happened, so treating, for example, the spy George Eliot's claims against the secular priest John Paine as factual is highly questionable, particularly given Paine's own protestations sent directly to the queen. Spies said things that they knew would attract the attention of the authorities and that is important, but to treat their words as accurate is risky, as shown by, for example, discussion of a Benedictine friar (p. 159), a novelty never known to have existed, or the report that a monk assassinated Henri iii (p. 141) rather than a deranged Dominican friar.

There is certainly much to chew over in this book and Muller's successful reintegration of the international dimension of the excommunication, as well as her highlighting the public element of its impact, is wholly welcome.