Foreign policy involves a lot more than simply memorizing the principal products of Oman or the second verse of the Chad national anthem. Our foreign policy, we have learned, involves much in the way of sending signals. Depending on what they are and who is sending them, these signals can either confound our traditional allies or reassure them. Mixed signals, which are probably the worst kind, encourage our adversaries. Our foreign policy should be coherent, consistent and credible. And so too, to avoid chaos and confusion, should be the foreign policy and defense signals we send.

Lately the Reagan administration has been mixing its signals like a salad. While Pentagon budgets wax and while the Soviets are tongue-lashed for their large part in the rape of Poland, the Reagan Justice Department suspends any efforts to prosecute any of the 300,000 young Americans who, this year alone, have failed to register for the draft. Federal law requires men to register at their local post offices within 30 days of their 18th birthday.

But this year nearly one-fourth of the nation's 18 year-old men failed to register and were told by the Justice Department not to worry about the crime they committed. As signals go, that one is known as an audible.

Certainly that unmistakable signal must have been picked up by our allies, most of whom we are weekly exhorting to make greater national sacrifices of their own for our collective security, and the Soviets. The administration's announced decision not to enforce the registration law tells all involved--the Soviets, our allies, and ourselves-- more than a little about our national resolve at a time of international crisis.

When Ronald Reagan was a college student, there were no draft deferments. There was no draft. The United States, then, had the 16th largest army in the world. Turkey, Spain, and Romania all had more men under arms and more interest in European affairs than did the United States. But a second world war and a first cold war changed all of that. Today when two conservative senators from Utah and Nevada publicly object to our nation's MX missiles being placed in their home states, we soon discover that there are many German and British "Mormons" who feel the very same way about their own back yards. Everything is now a signal of some kind.

More important than any lofty rhetoric right now is the legal reality: the selective service law, on the books, can be broken with total impunity. The United States will apparently continue in its reliance upon the discredited and undemocratic volunteer military force.

Reagan's supporters in this benighted policy are his old foes, the anti-Vietnam folks, who are now most concerned about a possible U.S. entry into El Salvador. What the peace folks somehow do not grasp is that their ranks were swelled during the Vietnam days precisely because there was a draft. In fact, one survey conducted after the 1968 Iowa caucuses, in which Eugene McCarthy scored surprisingly well, revealed that a large majority of the anti-war political newcomers had one characteristic in common--they had a son or brother who was at draft age or approaching it. A draft means more people with a personal stake in the nation's foreign policy.

But the strongest argument for returning to the draft is the one made by a thoughtful American patriot, retired Army Col. John Keeley. To do so, in Keeley's judgment, would mean that "the nation would put an end to the demeaning attempt to buy its security through the economic dragooning of the poorest and dumbest of its people."

Then, says Keeley, "we will have faced squarely the obligation that no self-respecting society should ever deny--that service to country is an obligation to be assumed by the best and the brightest of society." Now, that's a signal worth sending, both domestically and internationally. And a very clear signal to all involved.