The 1987 Constitution expressly requires Senate approval for a treaty to become "valid and effective" but is silent on treaty withdrawal. President Rodrigo Duterte has seized upon the textual gap to withdraw the country from the Visiting Forces Agreement with the United States of America, without Senate approval. On March 20, 2020, the Senate majority bloc, for the first time in history, opposed Dutertian rule and argued that because the Constitution requires Senate concurrence for treaty conclusion, senatorial imprimatur is likewise needed for treaty termination. Neither of these views finds its place in Philippine constitutional order. But while their ends conflict, the error is shared: an overreliance on legal text. On one hand, the Senate rightfully invokes the separation of powers, yet unduly limits that constitutional principle to constitutional provisions. On the other hand, the President ignores how the gray in-betweens of black letter law have long been filled by an unwritten yet time-honored principle. This paper provides a third approach. By shifting the focus from the written text to the unwritten tenet, the paper defines the limits to a presidential treaty power free from the faults of Philippine formalism.