Differences in doctrine and worship that divide Christian churches -- and how to overcome these -- have drawn much ecumenical attention over the years. There has been far less discussion of how the quest for Christian unity is helped or hindered by the legal structures and forms by which churches organize themselves. In most Christian traditions canon law (or church order) has strengthened confessional identity and distinctiveness, taking little account of new realities emerging from the quest for the unity of the church -- common witness and collaboration, a sense of community and mutual accountability, agreements over historic theological disputes, fresh understandings of church-state relations and the establishment of ecumenical organizations. After outlining the historical development of church legislation in Protestant, Orthodox and Catholic traditions, the author explores what ecumenism implies for this central but often neglected element of church life.