The foreign minister of Chile, Juan Gabriel Valdes, came to Washington last week, bringing with him unwelcome reminders of the case of Gen. Augusto Pinochet, the former president and tyrant who terrorized his countrymen for 17 pitiless years and who was called on the carpet last year by a Spanish magistrate.

Pinochet, now 83, says he enjoys full immunity as a senator for life and former head of state. He remains nonetheless under house arrest in London, awaiting the British home secretary's final action on an extradition request from Spain, where a judge takes the novel position that Pinochet should pay for his crimes against humanity--specifically against Spaniards, who, like thousands of Chileans, were imprisoned, tortured, kidnapped or "disappeared" in accordance with Pinochet's view of national security.

Britain's surprise action caused enormous consternation in chanceries around the world. Dictators who are untouchable in their own countries must have become leery of foreign travel. Who knows what human rights fanatic with a warrant is lurking in the potted palms of fashionable continental hotels?

There is much huffing and puffing about the principle of sovereignty being violated. There is indignation that Spain, which coddled its own dictator, Francisco Franco, right to the end, and sought his permission to restore the monarchy that has led to democracy, is exercising moral judgment on a foreigner.

The foreign policy implications are incalculable. What if other nations stand in judgment on a unilateral action, suddenly viewing it through the focus of international law and accords against violence and torture?

"We hear so often the 'poor Henry' argument," says Carlos Salinas, a Chilean-born human rights advocate at Amnesty International. The worry is that Henry Kissinger, for example, former U.S. secretary of state, might not be able to go abroad without fear of being nabbed by some nationalist with a grievance. Kissinger was, of course, the principal architect of the U.S. "destabilization" program that helped facilitate the advent of Pinochet.

Minister Valdes, the press was told in advance, would lay a wreath at Sheridan Circle at noon last Monday, the site of a local Pinochet-era atrocity, the car bombing of Orlando Letelier, a distinguished dissident and former ambassador of Chile. He was killed on Sept. 21, 1976. With him in the car was his assistant, Ronni Moffit, a 25-year-old U.S. citizen.

Valdes was a friend and protege of Letelier. Together at the Institute for Policy Studies, a left-of-center Washington think tank, they used to provide a steady, up-to-the-minute flow of information about the abuses in their native country at the time. After the murders, Valdes fled.

The extradition hearing for Pinochet is set for Sept. 27.

Curiously, the United States has no official position on whether or not Pinochet should be tried.

In a news conference devoted mostly to trade, Valdes talked vaguely about a possible trial in Chile, and hinted that a U.S. trial would be better than one in Spain. Of the three prime candidates, Spain, Chile and Washington, Washington is clearly the cleanest, least complicated, least fraught locale.

According to Lawrence Barcella, a former Justice Department prosecutor who spent 10 years as chief of the department's investigation into the Letelier-Moffit case, the inquiry did not establish conclusively that Pinochet ordered the murders. Barcella is convinced that he did, but was unable to turn up hard evidence. But in a much-remarked-upon opinion piece in The Washington Post last December, he stung former Justice colleagues by suggesting a want of zeal in their pursuit of Pinochet.

"If a person in Chile kills someone in the U.S., it is a very clear-cut case of violation of our laws," says Barcella. "There are no international charters to adjudicate, no foreign policy considerations. It's a case of thuggery, and if we don't proceed, we are telling terrorists who commit murder here on our citizens there is no reason to stop."

If he were still in charge, said Barcella, who is now in private practice, he would ask Chile for permission to interview Gen. Manuel Contreras, former chief of Chile's notorious secret security agency, DINA. Contreras, doing time in Chile for the Letelier-Moffit murders, gave an affidavit in which he stated everything he did was on direct orders from Pinochet. He made no reference to the bombing. Barcella says he should be asked.

The Justice Department won't discuss the case because, it says, the investigation is still in progress.

Pinochet is old, say his defenders. Chile, they say, is a fragile democracy and might not survive the trauma of seeing in the dock the monster Chileans think saved them from communism. Chile has found peace. Barcella and the human rights people think it should seek justice as well. The United States should take the lead in showing that the two are not incompatible.