Ever since the rescue mission fiasco in Iran, Congress and the White House have been arguing over the president's responsibility to inform key members of Congress before undertaking military action that might lead to war.

Under the Constitution, only Congress can declare war. But the legislators effectively relinquished thier authority during the early years of the Vietnam War. In an effort to recover its abdicated responsibility, Congress in 1973 passed the War Powers Act.

The law supposedly was a brake on future military adventures by a president requiring him to share his plans with Congress before committing the nation's armed forces in a given situation. But the law was worded vaguely enough to give the White House lawyers at least arguable loopholes to justify the secrecy of the Iranian opperation.

The crucial provision of the War Powers Act states: "The President in every possible instance shall consult with Congress before introducing United States armed forces into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances . . ."

The law was sponsored by Sen. JacobJavits of New York, ranking Republican on the Foreign Relations Committee. In April, alarmed by rumors of a military solution to the hostage crisis, Javits and Sen. Frank Church (D-Idaho), the committee chairman, wrote privately to Carter, reminding him of his obligations under the War Powers Act. The letter was delivered six hours before the rescue mission was launched.

"They were concerned about jungle drums, about military action," as one source put it. Both senators thought the president was planning military strikes against Iran.

Part of the administration's post-raid excuse for not consulting with Congress was that the rescue mission was not really a military operation but a "humanitarian" effort to free illegally held American citizens. But, in fact, as my reporter Ron McRae has established, outright military strikes against the Iranians were planned for the second and third stages of the rescue mission. The only reason the operation did not become undisguisedly military in scope and execution is that is was aborted in the primary stage because of helicopter failures.

In private and in public, Carter and Attorney General Benjamin Civiletti have fallen back on another contention they made in the rescue-mission debate: the need for secrecy forces a president to wriggle through the "every possible instance" loophole of the War Powers Act. It is simply not possible, they argue, to consult Congress about an operation and have it remain secret. Word would leak out and the operation would have to be canceled.

In the April "instance" only Senate Majority Leader Robert Bryd was informed of the rescue mission -- and hewas told about it only the day before it began. He said later he had had no idea the action was so imminent.

In the emotionally charged atmosphere following the aborted mission, no one in Congress wanted to appear less than totally committed to the cause of freeing the hostages -- particularly given the impatient, truculent mood of the public as reflected in opinion surveys. So the debate was reduced to what one observer characterized as "legalistic wrangling."

While insisting on its "right" to take emergency action without consulting Congress, the White House has clearly been seeking to get the kind of congressional support that would prevent recriminations after a future operation.

For example, the White House has been pressuring two members of the Intelligence Committee, Sens. Birch Bayh (D-Ind.) and Walter Huddleston (D-Ky.) to engage in a "colloquy" on the Senate floor supporting the president's stand against prior consultation. In senatorial parlance, a colloquy is a form of prearranged, friendly debate that is often simply inserted into the record unspoken. In this case, it would give Carter something to point to later as evidence of support from outside the White House. But so far, Bayh and Huddleston have not gone along with the idea.

The hawkish Senate Armed Services Committee was persuaded to vote down an amendment to the War Powers Act that reaffirmed the prior notification requirement. But Sen. J. James Exon (D-Neb.) went to the Senate floor and won reaffirmation of the disclosure requirement after intense debate.

White House sources admit that Carter's main worry is that a minimum requirement of the reaffirmed War Powers Act, and the new Intelligence Oversight Act, would be that he inform the Senate Minority leader in advance of a planned operation. The current minority leader, Sen. Howard Baker of Tennessee, is far from a White House team player.