Mitsuo Matsushita has shown an abiding interest in the systemic problems faced by the multilateral trading system. This tribute explores the significance of Article 31(1)(3)(c) of the Vienna Convention, the Systemic Integration Clause, of the Vienna Convention on the Law of Treaties to these concerns. While the place of the clause in the WTO acquis is already accepted, and its basic implications are well understood, its true scope and potential remain largely matters of conjecture. This brief chapter revisits past discussions of how the clause potentially supplies a broader and more flexible rule than GATT Article XX’s General Exceptions Clause in resolving conflicts with other, non-trading concerns. It could still prove useful when trade lawyers address increasingly complex conflicts between the WTO legal system and the regional, and increasingly mega-regional and comprehensive, trading obligations of WTO members. Today, such festering concerns demand a functional analysis of the uses of the Systemic Integration Clause.