Between 2013 and 2016 Norman Doe and Mark Hill convened the Principles of Christian Law project, which brought together theologians, jurists and church leaders from denominations within many of the major Christian traditions. The first phase of their work culminated in the publication, in 2016, of the Statement of Principles of Christian Law. The purpose of the project was ecumenical – working to explore how church law could be a powerful tool for unity. It responded to the paucity of literature engaging in a comparative study of law and religion, to the failure of the ecumenical movement more generally to grapple with the ways in which law influences and forms relationships between churches, and the apparent failure of theologians and lawyers to work together and to recognise the huge role which church law could play in promoting ecumenical endeavours. In doing so, it ran counter to earlier ecumenical initiatives, which had focused on divergence rather than congruity, concentrating on law as a source of unity rather than of difference.

The Principles of Christian Law project took as its starting point the principle that church law exists to further the mission of the Church, that it is strongly underpinned by theology and that an understanding of it is vital to a meaningful self-understanding of Christianity, the structure and regulation of the Christian life and thus the true nature of ecumenical efforts. In working towards the 2016 Statement through shared conversations and attentive listening, it built upon a consensus that there are principles of church law common to all traditions, and that churches contribute to these principles, which are dynamic and capable of further development, through their own regulatory instruments.

If the first phase of the project was concluded by the publication of the Statement of Principles of Christian Law, this volume marks the next phase in the development of its work. In it, theologians, jurists and church leaders, most of whom were members of the panel of experts which formulated the 2016 Statement, begin the process of responding to that statement and considering the reception of its common principles into each church. The chapters focus on the internal religious laws from bodies across the Christian traditions, drawing in matters of external (church–state) relations where appropriate to the setting of the body in question. Each chapter considers the sources and forms of church law, order or polity, the subjects comprehended by that law, order or polity, the people upon whom they are binding, the foundations or reasons for legal rules, and the extent to which the body uses principles of law, order or polity. Each chapter then concludes with an evaluation of the relationship between tradition-specific laws and the 2016 Statement.

As I sit and ponder my response to this volume I am struck, above all, by its distinctiveness in its attitude to law. Rarely – at least in the Anglican tradition – does one come across accounts of church law which cast it in a positive light. It is more usual, indeed, to celebrate the supposed absence of law or effective legal regulation as safeguarding liberty and comprehension. Similarly, as already noted, ecumenism has more often been marked by a conviction that law is a source of division than by a recognition of its possibilities as a source of unity. This volume is, then, almost counter-cultural in its willingness to embrace the benevolent potential of church law and to conceive of it as a fundamental source of unity and the lynchpin of effective ecumenism. Its chapters embrace church law as expressing the doctrine of churches, and as facilitating and regulating their communal life and the fulfilment of their mission. In doing so, they powerfully demonstrate the common foundations and shared inheritance of traditions which at first glance stand in stark contrast to one another. In the words of Grand Ecclesiarch Aetios (Dimitrios Nikiforios) in his conclusion to the volume, the 2016 Statement ‘transcends the mere habit of separation, learnt from centuries of being out of communion, highlighting the common rule of faith as an authentic expression of the shared Christian identity’ (p 255).

Something else which must inevitably strike the reader of this volume is just how much law there is, even in churches which one would not immediately associate with a particularly law-based approach to the arrangement and regulation of their corporate life. It may address different concerns or agendas in different contexts, and its precise form and mode of enforcement differs from one tradition to another, but law is everywhere. It regulates the functions of each church's community, the conduct of members, the use of property and, in many instances, the church's relationship with the state. This is true even where the theology of the church in question is prima facie ambivalent or hostile towards the role of law in the life of the church. It seems that there is no escape from the law or legalistic approaches to the regulation of collective life and endeavour.

This brings us to one of the great strengths of this volume. In bringing together theologians and jurists from a range of traditions to write about their own legal systems, and to respond to the 2016 Statement in the light of those systems, it provides a wonderful whistle-stop tour of the legal systems of the major denominations. This is useful in and of itself, but the accounts given are not merely informative but in many instances profoundly evocative in terms of helping the reader to a deep understanding of different churches and the role that law plays within them. The chapters offer fascinating insights into the ethos and culture of the churches included, their approaches to polity, and the things that concern them. Above all, and speaking to the dual characteristics of churches as both temporal entities rooted in a particular time and place, and spiritual bodies living out a spiritual commission, the chapters demonstrate not only the common foundations of church law as an expression of Christian doctrine but also the distinctive character of local arrangements in consequence of the impact of history and culture.

Here, for me, lies the fundamental appeal of this volume. Time and again, it provides glimpses of that strange combination of agency and contingency with which the legal historian and comparative lawyer are so familiar – that balance between law as shaping the world in which we live, as a matter of positive choice, and law as a product of history and happenstance, responding to and constrained by circumstance. This is not a coldly clinical exploration of a purely mechanistic set of systems. Rather, it is an exposition of different lived realities, shaped by the fortunes and ideologies, the circumstances and the aspirations of Christians across the world and through time. As a living embodiment of ‘law and society’, the book has much to commend itself to a broad academic audience, in its accounts of law and legal frameworks shaped by historical, political and geographical contexts. As a study in comparative law, its potential as a tool for ecumenical effort is hard to overstate. The chapters help Christians to understand one another better as they look across at other traditions. They help them better to remember what binds them together, and better to understand what is a matter of principle or deliberate choice, what is a question of preference and what is a consequence of historical necessity. As the different traditions embark on this next stage of the Principles in Christian Law project, this will help them to understand better the choices and responses they make, and the real significance and potential of these.