The author studies the communitarian and conventional models of legal integration used in the European Union (EU) and the Eurasian Economic Union (EAEU), respectively. The purpose of this comparative legal analysis is to determine unique features reflecting differences between these models. Particular focus is on the examination of legal acts of public bodies of the EU and the EAEU — their legal nature, place, role and the characteristics of their implementation in the national legal systems of their members. The author also analyses how the Court of the European Union and the Court of the Eurasian Economic Union control the enforcement of legislation of the EU and the EAEU, primarily in those cases where the courts assess justifications provided by supranational public bodies of these unions when they pass legal acts creating rights and obligations directly for citizens of the EU and economic entities of the EAEU. The article offers a rationale for the concept stating that the absolute priority of integration law over national legislation and the binding power of decisions of a supranational court for all participants of integration relations are the key milestones of supranational legal integration; when these milestones are achieved, it is possible to open borders not only for economic cooperation, but also for other forms of collaboration not linked tightly to the general processes of transnationalization of the economies.