THERE'S A MOVE in Congress to finesse the current stalemate over the War Powers Act by setting up a commission to rework the law. It could be useful, but something basic needs to be better understood first. The premise of a commission is that there are flaws in the War Powers Resolution, as it is called, and that Congress with 14 years of experience under the law can now set matters right. But more is involved than tinkering over terms of presidential notice and congressional sanction. The problem is of another sort.

By the War Powers Act of 1973, Congress intended to rule out any more presidentially declared wars like Vietnam. But the law, formalizing consultation, reflected less some ultimate and unappealable constitutional wisdom than a political condition of presidential enfeeblement and congressional agitation. It is now said, and not only by partisans of presidential discretion, that the law fits poorly the gray-area conflicts in which the United States finds itself involved. But what the law really fits poorly are the changed political circumstances.

The presidency has gotten relatively stronger. Richard Nixon could not keep Congress from passing the War Powers Act over his veto, but Ronald Reagan has kept Congress from applying even a diluted, single-use, policy-friendly version of the law in the Persian Gulf. There is much merit in the stated rationale for the War Powers Act -- that under its terms a president can consult Congress and strengthen his hand. But in practice the executive branch is zealous in asserting its prerogatives and Congress alternately and sometimes simultaneously zealous and uncertain. This is how the present, rather embarrassing impasse was reached.

In fact, 200 years of history under the Constitution shows that conflict over ''war powers'' has been continuous and unending. Far from being a temporary and unfortunate accident of the day, conflict is built into the basic checks and balances of the Constitution and into its very language, which necessarily is sufficiently broad to prevent any settled and final resolution. This is the basis of the assertion that the Constitution is an invitation to struggle for the privilege of directing American foreign policy.

There must be guidelines: Congress should realize the plain limitations on its operational capabilities and the president should realize the value of congressional support. It is first of all by political decisiveness, however, not by legislative craft, that these guidelines can be best applied.