Welsh jurist and Anglican theologian Norman Doe has pioneered the modern study of comparative ‘Christian law’, analysing the wide variety of internal religious legal systems governing Catholic, Orthodox and Protestant churches worldwide. For Doe, religious law is the backbone of Christian ecclesiology and ecumenism. Despite the deep theological differences that have long divided Christian churches and denominations, he argues, every church – whether an individual congregation or a global denomination – uses law to balance its spiritual and structural dimensions and to keep it straight and strong, especially in times of crisis. This makes church law a fundamental but under-utilised instrument of Christian identity and denominationalism, but also unity and collaboration on many matters of public and private spiritual life, both clerical and lay. Doe has developed this thesis in a series of impressive scholarly projects and books – first on Anglican law, then comparative Anglican-Catholic canon law, then all Christian laws and other Abrahamic laws, and their interaction with secular legal systems. This article offers an appreciative analysis of the development of Professor Doe's scholarship, and situates his work within the broader global field of law and religion studies.