Courtesy of one of the most generous leaks ever to cascade out of a meeting of the National Security Council (what former State Department spokesman Hodding Carter III would call "a direct arterial bleed"), there is no mystery about the manner in which President Reagan renewed hostilities against the Soviet natural gas pipeline to Western Europe: he did it boldly, incisively and over the namby-pamby objections of a conveniently absent Al Haig.

There is, accordingly, a lot less mystery about why Haig jumped ship. The pipeline decision was only a slap at Haig policy. But the leak, it turns out, was the last in a long series of calculated shivs in the shoulder blade from the White House crowd. Together, they nicely illustrate in retrospect all the elements -- pride, personality, politics -- that had brought the Haig-White House relationship to an irreparably rancid state.

The anonymous but ahthoritative leaks to The New York Times had the Leader of the Free World (LFW) coolly staring down a passel of free-traders, Europe-freaks and appeasers who were too weak-kneed for real economic warfare against the Soviets. Enough of "words," the LFW is said to have cried (or something to that effect); he had called on the Soviets to come up with "deeds"; the LFW could do no less.

And so he came down on the side of Defense and national security adviser William Clark. The United States would not only refuse to relax its sanctions on participation of any American firms in the building of the pipeline, as U.S. business interests have been requesting. The United States would go further and seek to extend the sanctions to include U.S. subsidiaries in Europe and European licensees of American industrial technology. This tightening of the screws effectively reversed what the Europeans had every good reason to believe was U.S. policy.

And the irony is that Haig has already been proven at least half-way right, as witness the shouts of defiance from the West German and other wounded European parties. The effect is to damage, if not demolish, precisely what the president was trying to build on his European tour: confidence in the measured strength of Ronald Reagan's statecraft; allied firmness and likemindedness in the face of the Soviet threat.

So why did he do it? The explanation begins with an almost theological confidence on the part of a handful of Reagan advisers in the efficacy of economic sanctions against the Soviets. In shorthand: Soviets crack down on Poland; United States signals protest with sanctions on U.S. trade and calls on allies to do the same; Europeans drag heels; clampdown on Poland continues; Reagan goes to Versailles to push partners for credit restraints against Soviets, gets dusty answer; Reagan sees original signal weakening. (Republican Right also sees Reagan weakening.) So Reagan reaches out to throttle the pipeline -- to show the Soviets (and anybody else) who's tough.

The only trouble is that he is far more likely to show the Soviets who's weak. The French and the West Germans, particularly, have a heavy investment -- emotionally and politically as well as commercially -- in the pipeline. With unemployment as high, or higher, than ours, they value the jobs tied to the pipeline's production. They also value the alternative energy source. They can fight back, and they insist they will.

Nobody in the administration likes the pipeline. It would earn the Soviets sorely needed hard currency and theoretically weaken the Europeans by increasing their dependency on the Soviets for energy. But the project is well along. So the argument from the State Department (and Commerce) is really over practicalities. Is it worth the hassle, and the attendant spectacle of an enfeebling alliance disarray, to try to stop it?

More to the point, how much does it figure in Soviet calculations of their overriding security interests in Poland? Not much, if the recent record of the Polish repression says anything. When things were quiet, the Polish authorities eased up. When riots broke out this spring, the lid was hammered down. As they wheeled out the water cannons, it is not likely the oppressors of Polish freedom were anguishing over economic sanctions by the West. Nor would their anguish increase, even if the United States could persuasively signal a real threat that the pipeline will be blocked.

Since the prospect is just the opposite, the signal to the Soviets would seem to be that the United States not only can't tighten the economic squeeze in a serious way on its adversary; it can't even bring effective influence to bear on its friends.

That's something the White House Haig-baiters might ponder when they're through tossing their hats in the air. Even assuming an abrupt demonstration of extra toughness is what's wanted right now, there is reason in the record to believe that Haig's successor, George Shultz, may well be among those who ask themselves what's tough about setting yourself up for a fall at the hands of your allies.