The Pentagon is so leaky these days that the secretary of defense can't conduct a discussion of draft- registration enforcement without reading the transcript in his morning paper. That is deplorable; it is also revealing.

A transcript of the April 12 discussion indicates that in attacking registration delinquency the Reagan administration's gunpowder is damp. Half a million young men of draft age are unregistered, despite repeated warnings. But little, or little that is visible to the unaided eye, is being done about it.

Why not? At the April meeting, John Herrington, assistant secretary of the Navy for manpower, expressed the view that any prosecutions for registration evasion should be "quiet," pursued in the "right jurisdictions," that is "in Omaha or somewhere like that," rather than in New York or Chicago, where press attention might be called to them. "Not in the District of Columbia," chimed in Defense Secretary Caspar Weinberger.

Herrington was also afraid that "felony prosecutions at this time may have an awful lot to do with the anti- nuclear movement."

No one is at his best in a transcript.

From the outset, the U.S. experiment with an "all-volunteer" armed force--of which this comic episode is only one result--has been a military and social disaster. The volunteer Army is a military disaster because, as almost any field commander will tell you privately, it has led to lower standards of both performance and expectation. It is a social disaster because it leaves a fundamental obligation of democratic citizenship disproportionately to those least able to enjoy its corresponding benefits.

The political impulse underlying the abolition of the draft in the early '70s was the cynical (and false) belief that it was the fundamental cause of discontent with the war in Vietnam. This political impulse was embellished by the Gates Commission report, which predicted that a mercenary armed force would be not only superior but more prestigious. It is, alas, neither.

To this muddled mix, some Nixon administration heavy thinkers added a flavor of libertarian ideology, including the silly notion that it is oppressive to be required to serve in the military.

The Afghanistan invasion led President Carter to a painful reassessment of this soft approach to national preparedness and military obligation. He ordered a half-step back in the direction of Selective Service-- draft registration--but not before confusing the issue with gratuitous worry about sex discrimination. In Congress, where there is an abiding urge to evade the issues of military manpower and readiness, the "unfairness" of a registration without women was gratefully seized upon as the crux of the debate.

Now, of course, we have the continuing ambivalence of Ronald Reagan. He could not resist taking a crack at Carter's call for renewed registration. Now, as president, he lives with an embarrassing contradiction. He disapproves in principle what he chooses to favor as a necessity of law and prudence. Small wonder that his irresolution is reflected at the Pentagon.

The Pentagon transcript overflows with revealing implications. There is the suggestion that "selective prosecution," which is inescapable for practical reasons when the number of delinquents is so large, might be made even more selective (the Justice Department willing) for political and policy reasons.

There is the unwillingness to grapple firmly with the muddled anti- conscription sentiment that tends to flourish in great urban centers, where freedom is interpreted as a free ride.

Finally, there is the apprehension that this administration's zest for big- bang weapons might be disturbed by emphasizing the need to rebuild conventional military strength. There is no sign of reaction, here, to the sudden crisis in the Falkland Islands, although that episode shows that the need for ready forces can arise in unlikely places and altogether unexpectedly.

Wan and weak enforcement of the draft registration law is only one of government's current failures to make and execute decisive and coherent policy. If Omaha is soon as confused as New York, it will be small wonder.

Ironically, the morning newspaper that printed the Pentagon transcript also reported that Americans are unusually willing, among the citizens of major democracies, to bear arms in the national defense. Our timid officials are not only spooked. They are spooked by shadows.