The article builds an innovative theoretical framework with the goal of unveiling the preconditions allowing ICs to become engines of supranationality in different institutional and socio-political contexts. In so doing, the article nuances the theoretical approaches on the relationship between supranationality and supranational adjudication. The article focuses on the Central American Court of Justice (CACJ) and the Caribbean Court of Justice (CCJ), and it compares them with the Court of Justice of the EU (CJEU). Both the CACJ and the CCJ have been branded as institutional copies of the Luxembourg Court. The two Court have also borrowed key jurisprudential principles from the CJEU with the goal of expanding the reach of Central American and Caribbean Community laws. Despite this, both Courts have thus far failed to foster supranationality in their respective systems. This is because the conditions allowing ICs to become engines of integration lie for the most part outside the direct control of the judges, most notably, in other institutional, political, and societal actors, such as national judges, regional organs, legal and political elites, as well as academics. The article, hence, suggests that ICs can become engines of de facto supranationality only to the extent to which these are supported by a set of institutional, political, and societal pre-conditions allowing the concrete enforcement of the rulings of the IC at the regional and national levels.