A strong argument for the Equal Rights Amendment, we're often told, is that it will simplify the tedious process (which even curmudgeons approve in principle) of extending legal equality to women.

ERA is simple, all right; but that is also an argument against it. In some matters of government, complexity-- not simplicity--is desirable. If simplicity were a paramount constitutional value, we would all think better of lynch law.

Appropriately, perhaps, the ERA ratification fight has become a comedy of simplifications. It began in 1979 when Congress by simple majority vote extended the original seven-year deadline. In doing so it winked at Article V, which requires a two-thirds vote to submit constitutional amendments.

Now the three-year extension, as if by poetic justice, has run afoul of a federal judge with a drastically simple judicial philosophy. Judge Marion Callister of Idaho has ruled the three-year extension unconstitutional and also declared that a state may rescind its ratification whenever it pleases. He may eventually be overruled; meanwhile, he has upset the apple cart just as critical ratification votes are approaching in several states.

And his is a novel intervention. The U.S. Supreme Court has been far more cautious. It once said that Congress may, though it needn't, set a deadline for ratification. It has said almost nothing else over the years except that the mechanics of ratification constitute a "political question" for Congress to settle. Judge Callister finds it "more logical" for courts, "as a neutral third party," to settle disputes over the ways and means of ratification. He ignores difficulties that have vexed minds of some experience and complexity.

For instance, in the 1939 case of Coleman v. Miller, Chief Justice Charles Evans Hughes and his brethren were asked to say how long it is "reasonable" for a pending amendment to hang fire without losing its "vitality." Answering that question, said Hughes wisely, would involve "an appraisal of a great variety of relevant conditions, political, social and economic, which can hardly be said to be within the appropriate range of evidence receivable in a court of justice." Judge Callister, less modestly, thinks otherwise.

The National Organization for Women had sought Judge Callister's removal from the case--not because NOW anticipated his strikingly simple faith in judicial neutrality but because he is an official of the Mormon church. This too was a simple argument. Judge Callister is not, thank God, the only churchman on the bench; others, too, might in the same way be accused of confounding sectarian doctrine with the Constitution.

Indeed, the shabby imputation of religious prejudice to Judge Callister summons up all sorts of ancient hobgoblins: notably, the long-laid fear of Protestants that Catholics in office might take orders from the Pope.

All this simplicity in the ratification fight merely reminds one of the dubious simplicity of ERA itself, the instrument that begot the fight. If ratified, ERA will provide judges with a mighty scythe for cutting through tangles of social and economic legislation, some good and some bad, but not always in the most "neutral" spirit.

The Judge Callisters of this world will be deciding all sorts of issues involving, to recall Chief Justice Hughes' words, "an appraisal of a great variety of relevant conditions . . . which can hardly be said to be within the appropriate range of evidence receivable in a court of justice." Complicated social and political preferences, even some reasonable and enlightened ones, may not withstand the present inclination of federal judges to treat distinctions as potentially invidious discriminations.

Federal judges have already concocted a fancy way of analyzing classifications by sex. Such classifications are, in the lingo of the bench, "suspect" and must be justified by a "compelling state interest." ERA, it seems to me, would make it all but impossible to sustain any gender classifications at all. Many useful distinctions now made by legislators, with popular consent, would be unconstitutional.

The result would be simple, but in many cases far too simple for the larger good of a varied society. Were I a state legislator in a target state, I would reluctantly say no to ERA.