Congress passed the War Powers Act in 1973. Its provisions, in essence, give Congress a veto power over deployment of U.S. forces "where imminent involvement in hostilities is clearly indicated by the circumstances." On paper, the president is supposed to acknowledge that he is putting U.S. forces at risk under the act's terms. In practice, the lesson of Lebanon is that this only works with a president who wants to make it work.

The original idea made sense. It was to find some formula more sophisticated than a formal congressional declaration of war to deal with the restraint imposed in the nuclear age. The various forms of "limited war," it was thought, called for new forms of consultation and collaboration between the legislative and executive branches. That the War Powers Act was passed over President Nixon's veto is evidence that this spirit of reconciliation was not accepted from the start.

That it still was not accepted a decade later was amply demonstrated by the way the provisions of the law were used -- and abused -- in Lebanon. By means just short of outright duplicity, the Reagan administration maneuvered for months to evade the law's requirements by minimizing even the appearance of a combat mission that would have triggered the procedures of the War Powers Act. With some notable exceptions, congressional leaders rolled over rather than accept the responsibility and the political risk of second-guessing the president until, finally, actual Marine casualties shredded the administration's pretense that the "hostilities" test of the War Powers Act did not apply.

Now you can argue, as the Reagan administration does, that the law should be repealed -- that it is even unconstitutional. Or you can accept the conclusion of its proponents hat it didn't entirely flunk its first real test. In the end, a bargain was struck between the president and Congress. A War Powers resolution was enacted with an 18-month limit on the Marine deployment.

But no case can be made that in Lebanon the War Powers Act achieved its stated purpose: "To . . . insure that the collective judgment of both the Congress and the president will apply to the introduction of United States armed forces into hostilities . . ." On the contrary, in Lebanon the War Powers Act had just the opposite effect of inciting a power struggle between the executive branch and Congress and encouraging an administration hellbent on ignoring its requirements to violate military doctrine in a way that exposed the Marines to high risk.

The president's churlish acceptance of the compromise resolution, while rejecting any of its implications of a congressional right to tie his hands, cried out for thoughtful reassessment, after the fact. About a year ago, in language considerably more measured than he had used in private to leading members of Congress at the height of the crisis, Secretary Shultz said as much.

"How the Congress and the Executive Branch should interact in the field of foreign affairs, particularly in matters of great moment, is an extremely important issue," he told a congressional committee. He thought the subject "ought to be thoroughly discussed, preferably in an atmosphere not having to do with some particular action we are struggling with."

There was an effort by Sen. Arlen Specter (R-Pa.) to work out with the administration some sort of congressionally supported Supreme Court test of the War Powers Act. But the Justice Department said it wouldn't work. Talk of amending the act, or of a congressional review, has died away. Asked about his views the other day, President Reagan said it was something he -- or future presidents -- should take up directly with Congress. Fair enough. But if not now, when?