Barring an unlikely outbreak of peace in the Persian Gulf, last week's renewal of the rancid debate in Congress over whether to apply the constraints of the War Powers Act to the U.S. naval intervention in the fight between Iran and Iraq will not be the last. Which side wins may well depend on sheer chance -- on hits or misses in the wildly unpredictable ''tanker war.''

And it may not matter much. The War Powers Act was passed in 1973 over President Nixon's veto as a way of strengthening Congress' hand in any decision to send American combat forces into ''situations where imminent involvement in hostilities is clearly indicated.'' It calls for the president to ''consult'' in advance with Congress and would require the removal of the forces within 90 days in the absence of a congressional declaration of war or resolution of approval. Those in the Senate who are renewing the push to have the law applied as a matter of principle would be unlikely to try to force a humiliating U.S. withdrawal from the Gulf this late in the day.

As a practical matter, then, the outcome may be less significant than the dismal picture the debate will present of the way the U.S. government has gone about the serious business of deploying the largest armada since the Vietnam War in what has to be considered to be, right now, the most dangerous part of the planet.

You cannot spend a day as I did last week listening to learned discourse on ''The Constitution and Legislative-Executive Relations in International Affairs'' without concluding that the Persian Gulf performance of both the administration and the Congress has been a godawful way to commemorate the bicentennial of the Constitution.

Space does not permit full justice to the scholarly analyses of the prominent academics or the lively exchange between lawmakers and former executive officeholders assembled by the Georgetown Center for Strategic and International Studies. Suffice to say that the historians agreed the framers did not anticipate harmony: Indeed, they invited conflict and expected that their checks and balances would work no better than the spirit with which the two branches approached the exercise of their rights and responsibilities.

Even while insisting that the ''vital powers in international affairs were to be reserved to Congress,'' Arthur Schlesinger Jr. stressed the importance of ''partnership'': ''Neither branch of government has a divine right to prevail over the other.'' Congress cannot conduct foreign policy, he said, but presidents ''must understand that no foreign policy can last that is not founded on popular understanding and congressional consent.''

Another historian, James MacGregor Burns, didn't exactly disagree. But he did think ''we are playing games when we talk about better relations.'' The War Powers Act ''has certain potential advantages'' he said, but ''has had no practical impact.'' Former defense secretary James Schlesinger dismissed its restraints as ''asinine,'' and added: ''Can you imagine Congress pulling out forces, once engaged, on a rigid timetable?''

Lots of critics would agree. But nobody present could deny that it is the law of the land. So it hardly advances ''partnership'' when Defense Secretary Caspar Weinberger takes it upon himself to declare the War Powers Act ''unconstitutional.'' Nor are congressional critics coaxed into ''partnership'' when the White House proclaims that conditions of ''imminent hostilities'' do ''not obtain'' in the Gulf on the very day that Iraqi aircraft and Iranian warships hit seven commercial vessels.

Congress is scarcely blameless. As demonstrated by last week's 50-41 vote in the Senate, it shrinks from using its power to enforce the law that it wants the executive to invoke on its own initiative. But Congress has also been badly used. Sen. John Warner, ranking Republican on the Armed Services Committee, insisted that Congress had at least been properly notified in advance of the commitment to ''re-flag'' and escort Kuwaiti tankers.

But notification, it turns out on further inquiry, came from lower-level State Department officials. It was classified ''SecretSensitive'' and addressed to staff members of the Senate and House committees on armed services and foreign affairs. I'm told it was so innocuously phrased (it spoke vaguely of ''cooperative, protective arrangements'' with Kuwait without even mentioning ''re-flagging'') that it was not thought worthy of the attention of committee members. Its conditional tense is said to have left the impression that no final decision had been made.

Yet there is clear evidence that at the time of the first ''notification'' on March 19, the ''re-flagging'' commitment to Kuwait had already been made. If that is the Reagan administration's sense of what constitutes ''notification,'' it is not hard to understand the uncommonly low state of its constitutional relationship with Congress or to identify what is so sorely lacking.

James Schlesinger and House Majority Leader Tom Foley gave the Georgetown Center's gathering the answer in only slightly different ways: What's missing is even a bare minimum of the necessary mutual trust.