There may be no one left to bring charges, nor a court system in which to try the case, but nuclear war, argues one group of attorneys, is nevertheless against the law.

In fact, there is no specific law against attacking an enemy country with nuclear weapons, they concede. But, say members of the Lawyers Committee on Nuclear Policy, preparations that could lead to the atomic annihilation of millions of civilians violate numerous international conventions governing the fighting of wars.

The New York-based committee, whose organizing efforts are just beginning, consists of about 20 law professors and practicing attorneys. Yesterday a group of about 25 international lawyers gathered here at the International Hotel in Washington to hear spokesmen for the committee make the legal case against nuclear proliferation.

Following in the footsteps of doctors, scientists and other professionals who have organized to seek a solution to the unthinkable, the attorneys see the law as one field in which they are uniquely qualified to forestall The End.

"Doctors say it's unhealthy. Scientists say it's destructive. What do you expect lawyers to say," said Robert J. Rhudy, a Harford County attorney who is spearheading the group's efforts to draw Washington-area lawyers into the fight.

"We are, in a sense, the high priests of civil order," said University of Iowa professor Burns H. Weston. "Nuclear weapons are fundamentally antithetical to everything that international laws stand for."

Judging from yesterday's debate, it may be a long time before the lawyers' case ever gets beyond preliminary arguments and into trial. There appeared to be little agreement on the law, and even less on what the group's courtroom tactics would be.

One participant suggested the Soviets are hell-bent on world dominance and can't be trusted. Another said that the group's legal counterparts in the Soviet Union can't speak their minds.

What the committee should be arguing, said a third, an instructor at the Naval War College, is that without a legal ruling on atomic war, individuals responsible for pushing the buttons won't know what to do when the time comes. As a result, he argued, all the military plans laid in advance would literally go up in smoke.

Organizers for the committee acknowledge that if the legal appeal seems somewhat fanciful, well, it probably is.

"The argument won't get us very far," Weston said. "But we should make that argument, nevertheless."

What the group offers, said Harvard University professor Roger Fisher, is experience in settling disputes. "The problem is not in the weapons," he said. "It's in our heads. There is no way we're going to wake up one morning without conflict. Conflict is a growth industry."

If the Russians and Americans would sit down like lawyers and talk business, instead of threatening to cut each other's throat, they might be able to iron things out, Fisher suggested.

Rhudy said that what the group suffers from is not a lack of principles, but manpower.

"It's been getting its academic wagons in a circle," he said. "But it eventually has to go out and get the rank and file lawyers across the country to join."