This article examines a dilemma facing architects of transitional justice processes within the framework of a permanent constitution. According to the dilemma, if the transition is successful the permanent constitution is replaced; if the permanent constitution remains in place, the transition is rendered impossible. The dilemma is illustrated by the ‘constitutional replacement doctrine’ of the Colombian Constitutional Court, which has held that constitutional amendments (including transitional justice mechanisms) which ‘replace’ essential principles of the constitution are a species of ‘unconstitutional constitutional amendment’ and are invalid. There is undeniable logic to this doctrine—a constitutional change which degrades the fabric of a constitution by ousting its underlying principles should require the enactment of a new constitution, rather than a process of amendment. However, applied in a rigid fashion, doctrines of this sort render processes of transitional justice within the framework of a permanent constitution impossible. This in turn presents a major obstacle for both transitional justice and constitutionalism in post-conflict societies. The recent jurisprudence of the Constitutional Court applying the ‘replacement doctrine’ to the current peace process with the Armed Revolutionary Force of Colombia, however, suggests a middle way: transitional constitutional amendments which might trigger the doctrine are nonetheless constitutional if they are enacted consistently with the international and transnational framework for transitional justice, assessed by means of a balancing test, whereas a strict syllogistic application of the doctrine is called only for in cases of suspected ‘abusive constitutionalism’. This article analyzes and endorses the Constitutional Court's revised doctrine. The solution presented here recognizes that, although the design of a successful process of transitional justice is likely to ‘replace’ the existing constitution with something substantially different, it should be regarded as ‘constitutional’ if the transitional justice mechanisms only limit essential principles of the permanent constitution in the degree that is required for the adopted mechanisms to achieve their goals. The result is an internationally nuanced notion of ‘transitional constitutionalism’.