This study examines how the Argentine Supreme Court controls the domestic validity of international treaties through a rigorous formalist doctrine. It posits that the Court has constructed a “complex federal act” requiring three constitutive stages—executive signature, congressional approval, and executive ratification with international deposit—as a sine qua non for any treaty's domestic applicability. Through doctrinal analysis of landmark cases including Ekmekdjian (1992) and the watershed Acevedo ruling (2025), the study finds that the Court prioritizes procedural constitutional fidelity over legal certainty derived from its own prior precedent. The results reveal a judicial strategy that asserts ultimate authority over the gateway for international law, conditioning validity before any substantive application may occur.