EACH TIME the Supreme Court deals with the subject of obscenity, the need for a general overhaul of the law becomes more obvious. Last Monday, for instance, the Court upheld the conviction of Jerry Lee Smith of Iowa and the three-month prison term imposed on him. His crime was sending through the mail - instead of delivering by hand or by freight - some magazines and pictures that postal inspectors, using fictitious names, had ordered. The decision, while a logical extension of past Court rulings, creates a remarkable situation. The federal government is now in the position of telling the people of Iowa that they cannot legally obtain through the mail publications and films they request even though their state government says they can buy the same material at shops and stores.

That situation arises because in Iowa it is a crime to distribute obscene material to minors, but not to adults. Thus, even if his magazines and pictures were obscene (something he disputed), Mr. Smith could have sold them to those postal inspectors without being prosecuted. But, under the Comstock Act passed by Congress in 1873, once he put those publications into the mail he had committed a federal crime if a jury decided subsequently they were obscene. However, because of the way in which the Supreme Court has said juries are to decise such questions, there is no way of knowing in advance whether particular material is obscene. It all depends on the jurors chosen to hear the case. They are instructed, each time, to apply "the standards of their community" in determining whether the material in question "appeals to the prurient interest" and depicts sexual conduct in a "patently offensive way." Thus, the same magazines and films can be ruled obscene in Des Moines and not obscene in Iowa City.

To sum it up, you can now commit a federal crime by mailing certain material from Iowa City to Des Moines even though you bought that material legally in an Iowa City store. You may not think the material in obscene, but you cannot be sure of that. If the post office thinks it is, the jury chosen to hear the charge against you will decide.But even if that jury decides that material is obscene, you can continue to buy it legally in Iowa City. You may even be able to mail it to your friend from some other city without committing another crime because the jury in that other city may not find it obscene.

That, we submit, is absurd. It is time for both the Court and Congress to try to make sense of the situation. We commend to both the dissenting opinion of Justice John Paul Stevens in this case. His attack on the constitutionality of obscenity laws is, to us, unanswerable, and his suggestion that regulation in this area be approached in terms of abating nuisances, rather than chasing criminals, is worth exploration. A hundred years of trying to stamp out dirty books and pictures by prosecuting their purveyors is enough. We should regulate where and how this material is sold and rely in the long run, as Justice Stevens suggests, on "the capacity of the free marketplace of ideas to distinguish that which is useful or beautiful from that which is ugly or worthless."