ALTHOUGH ONLY 10 days have passed since the Supreme Court ruled that some criminal proceedings can be conducted in secret, lower court judges have already provided a demonstration of the sweep of that ruling. It is not encouraging. For it suggests that judges are plenty eager to use their newly granted power and do their business behind closed doors.

In New York, for example, the highest court has said a judge was right to order a secret session despite a prosecutor's objection. In Virginia, the highest court has refused to review a judge's decision to conduct an entire murder trial in secret. In Buffalo, a judge has held a secret hearing on whether a nun should be charged with assaulting a pupil. And in New York City, a judge is considering a secret session on whether he should sentence a convicted criminal as a persistent offender.

Each of these cases seems to conflict with some of the limits on secrecy that either the Supreme Court appeared to be writing or two of its five-member majority suggested in separate opinions. The court said prosecutors must concur in requests for secret hearings. It also indicated that other methods of protecting juries from prejudicial information, such as sequestering them, should be used. One separate opinion suggested only pretrial hearings can be held in secret, not trials themselves. The other said judges should always consider the amount of publicity a particulra case is likely to generate.

The speed with which the lower court judges have brushed aside these limitations is frightening. So is the New York court's criticism of a trial judge for delaying proceedings while his secrecy order was appealed. The inference is that those judges regard secret sessions not only as the easiest and most efficient but also the best method of solving the difficult problem of prejudicial publicity. If that is the case, secrecy is likely to become commonplace in courts all over the country. Unless, of course, one member of the Supreme Court's slim majority can be persuaded he voted wrong on July 2.