"An attempt by any outside forces to gain control of the Persian Gulf region will be regarded as an assault on the vital interests of the United States. It will be repelled by use of any means necessary, including the use of force."

That's the basic Carter Doctrine: simple, direct, tough and unambigious. Had it been left at that in the president's State of the Union message last January, it might even have been taken as the clear signal it was supposed to be.

But it wasn't left at that. In addition to the economic "penalties" for the Soviets' Afghanistan invasion and the Olympic boycott, the administration's signal-senders offered one, immediate, attention-grabbing military measure. Carter would call on Congress for authority to reinstitute the draft.

When you look at what's happened with that proposal -- and at what practical purpose it would serve in speeding mobilization in an emergency -- you have to wonder whether the net effect may not be to undercut rather than reinforce the Carter Doctrine's intended demonstrtion of American resolve military readiness.

The president did not just talk about registration as such. While he expressed a "hope" that current defense needs could be met without actually resorting to conscription, he warned that "we. must be prepared for that possibility." The resulting outcry was predictable; only a few months earlier, Congress had resoundingly defeated the same sort of pre-mobilization registration plan.

So it was hardly surprising that the registration/draft issue should become an instant campaign issue -- with most major candidates, Republican as well as Democrat, solidly opposed. What sort of signal was that?

Women were to be included in the Carter proposal and so quite a different issue flared up -- an issue with no particular relation to any "clear and present danger to our national security."

Though polls showed the general public favorable to the idea of registration as a matter of principle, little enthusiasm was detected among the potential 19- and 20-year-old registrants. Anti-draft movements flowered, nourished by pacifist groups and the remnants of the Vietnam anti-war movements. The administration wobbled; delays set in; there were even reports of second thoughts from the Carter high command about the whole idea.

In Congress, there was brisk debate when the measure finally reached the floor, barely surviving a close House committee vote. In the Senate, a brief filibuster flared. Though the controversial inclusion of women was ultimately removed, the American Civil Liberties Union has taken that issue to the courts in a way that could conceivably invalidate the whole law.

It is true that draft registration was not the only military measure involve involved in the effort to give force to the Carter Doctrine. The president announced plans to pre-position supply ships in the Persian Gulf area; a new rapid deployment force is in the works. But the target date for much of this buildup is several years hence.

And it is also true that the registration program will proceed this summer. But there is at least some reason to ask what difference it will make. Before the president officially decided in favor of the plan, you could get a convincing argument at high levels in the Pentagon that registration would not hasten an actual draft in an emergency for a rather simple reason: it would take just as long to make room for draftees in existing training facilities as it would take to register and draft them.

Today, the same officials who were expressing deep reservations only a little more than six months ago are gamely coming up with reasons for thinking that, after all, "Why not?"

"It's one less thing to worry about if we do have to go to a draft," says one. "Snow or bad weather could foul up registration when you needed it in a hurry -- or the time for it might come when there was a shortage of gasoline.

This was we'll have the registration lists in hand."

Well, the chance of snow this summer is certainly unlikely, and gas lines do not seem probable. The best estimate is that most eligibles will dutifully show up at post offices to register their names and addresses without a fuss; the penalties for noncompliance are stiff.

But you still have to wonder whether either our allies or our adversaries will be much impressed. Still more profoundly do you have to question the strategic wisdom of this sort of semaphore approach to the conduct of foreign policy -- of running things up flagpoles when the people whose attention you most want to attract are unlikely even to notice, and still less likely to salute.