After the war in Vietnam, the Office of Legal Counsel continued its surgery on the WPR. In a major 1980 review of presidential power to use force without congressional authorization, the OLC argued that constitutional interpretation should be informed by the way presidents have exercised their powers. Substantive limitations on the president's broad power were “a function of historical practice and the political relationship between the President and Congress,” wrote Assistant Attorney General John M. Harmon. “Our history is replete with instances of presidential uses of military force abroad in the absence of prior congressional approval.” Notwithstanding persistent criticism of presidential overreach, the OLC viewed the history of executive power grabs as evidence of the constitutional scope of the commander-in-chief power.
In this important opinion, the OLC relied on the interpretive method referred to as “historical practice” or “the gloss of history.” This approach is based on the idea that interpretation of the separation of powers should be informed by the way the presidents and Congress have historically exercised their powers. The methodology became a key feature of executive branch legal opinions well before it received serious scholarly attention. OLC reliance on the gloss of history meant that the fact that a president had done something became evidence of the next president's power to do the same thing. For example, Truman's action in the Korean War is not treated as an outlier, but as legal precedent for unilateral presidential war power, at least for conflicts not exceeding the scope of that massive and destructive war. Because gloss of history analysis is a form of constitutional interpretation, it trumped acts of Congress like the War Powers Resolution, undermining Congress's ability to pull back on the broadening range of executive power.
If the War Powers Resolution was ineffective in placing limits on presidents’ ability to unilaterally initiate the use of force, what could it do? The WPR has consultation and reporting requirements. Section 3 states:
The President in every possible instance shall consult with Congress before introducing United States Armed Forces into hostilities or into situation where imminent involvement in hostilities is clearly indicated by the circumstances, and after every such introduction shall consult regularly with the Congress until United States Armed Forces are no longer engaged in hostilities or have been removed from such situations.