PRESIDENT REAGAN'S admiration for the "freedom fighters" currently attacking the Sandinistas led him the other day to state a "Reagan doctrine" that is sure to haunt him if he allows it to stand. Like the "Brezhnev doctrine," to which it bears an unfortunate family resemblance, it justifies a great power's decision to violate the sovereignty of other states.

Mr. Reagan got into the subject by observing that "there is a kind of bias in the treatment of guerrilla fighters. It depends on what kind of a government they are opposing." It sounded as though he were about to lay down a common standard by which all guerrillas should be judged.

Immediately, however, he drew a distinction between the "guerrillas" who, he said, are fighting the elected government of El Salvador not to bring freedom but to restrain freedom, and the "freedom fighters" in Nicaragua. What people refer to as "the government of Nicaragua," he said, came "out of the barrel of a gun. . . . Other than being in control of the capital, you might say, and having a handle on all the levers--what makes them any more a legitimate government than the people of Nicaragua who are asking for a chance to vote for the kind of government they want?"

Is Mr. Reagan asserting a right to encourage the overthrow of governments that take power by force and deny the vote? Few governments in the world would survive both tests. On the left, no sitting government led by a Marxist-Leninist party came to power by means other than revolution or coup, and none offers authentic elections. Is Mr. Reagan going to support Soviet and Chinese "freedom fighters"? Think of the many governments of the right that took and hold power by force alone. Is the president going to arm guerrillas against the regimes in Chile and Argentina?

In brief, the "Reagan doctrine" is a nonstarter. It shows that there is no good way to rationalize undermining governments with which one is not formally at war. Any effort to raise such a standard leads to logical absurdities and invites ambitious governments of other persuasions to develop their own lame and arbitrary excuses to play dirty.