THE SUPREME COURT seems to be drawing some important distinctions about the why government can limit pornography. On the one hand, it has sensibly let stand a lower court decision throwing out an overly broad antipornography statute that a coalition of feminists and traditionalists persuaded the city of Indianapolis to enact. On the other, it has upheld an ordinance by which the Seattle suburb of Renton, Wash., sought to cordon off "adult" theaters away from schools, parks and residential areas.

The Indianapolis ordinance was original to the point of wackiness. It states that pornography -- very broadly and vaguely defined -- is discrimination against women because "its effect is to deny women equal opportunities in society." It allows any woman to enforce it by bringing a lawsuit seeking injunctions and damages. It is designed to encourage vigilante censorship of material the Supreme Court has long ruled is not pornography. A federal appeals court said the statute amounted to "thought control" and threw it out. The Supreme Court declined to review that decision.

In the Renton case, Justice Rehnquist's opinion danced a little gingerly when it argued that the ordinance was addressed not to the content of the films but to the effects on the community of having such theaters in the neighborhood. But Justice Brennan in dissent is not more convincing when he argues that a local council can't limit adult theaters without expert testimony about their effects. Elected officials can be presumed to have a reasonable idea of the effects on a neighborhood of a pornographic theater, just as they do with a slaughterhouse or a drive-in movie.

Interestingly, neither the court nor the dissenters had much problem with defining "adult theater." By now, evidently, they all know one when they see one. In 1976 the court upheld a Detroit ordinance prohibiting concentration of pornographic theaters but with the majority unable to concur in a single opinion. This time the decision was a solid 7 to 2.

The court's decision does not deny that even pornographic movies may be protected by the First Amendment. But it allows a city to cordon them off from other neighborhoods. The practical effect of this decision may not be great, since X-rated videotapes and pornographic channels on cable television may put adult theaters out of business anyway. But it does seem that the court is reaching, without great strain, sensible results on a subject that has bedeviled it for more than two decades now.