Many reformed church orders, which reflect the Dort Church Order of 1619, albeit revised, still apply its subdivision into these four chapters: firstly, offices (dienste); secondly, general assemblies (samekomste); thirdly, doctrine, sacraments and other ceremonies (leer, sakramente en seremonies); and fourthly, church discipline (kerklike tug). This article focuses on the composition of church orders. The research question is the following: How are reformed church orders composed and what it the ecclesiological or juridical rationale behind this composition? This article contains paragraphs on the composition and the ecclesiological legitimisation of the Dort Church Order of 1619 and its predecessors, the reformed churches in the East-Indies (Batavia), the Algemeen Reglement of 1816, the Reformed Church Order of 1951, the church order of the Protestant Church in the Netherlands of 2004, and the major shift from the perspective of canon law to reformed church polity. Reformed church orders contain both doctrinal and disciplinary regulations in relation to three notae ecclesiae of a reformed church. However, there is more at issue than the theological nature of the composition of the Dort Church Order and its successors, namely their relation to the Institutes of Justinian.