The arrest of Gen. Augusto Pinochet, ruler of Chile from his 1973 military coup to his peaceful removal in 1990, is both a history lesson for U.S. interventionists and an argument for a world criminal court. Such a court could sort out the charges against a man said to be responsible for the deaths or disappearances of thousands of his fellow citizens.

The United States did not so much support Gen. Pinochet’s rise to power as oppose the socialism of his predessor, Salvador Allende. Jon Lee Anderson reports in The New Yorker that even before Mr. Allende took office, the Nixon administration authorized a “destabilization campaign” to unseat him. In a routine that future administrations would use elsewhere in South and Central America, the Nixon White House sent money and weapons to encourage the overthrow of the Allende government.

The result was Gen. Pinochet, who proved to be such an embarrassment to the United States that U.S. policy under Jimmy Carter was to plead with him to try democracy once in a while. Arrests and torture of political opponents, however, were more his style.

Now it is he who has been arrested, at a London clinic where he went for back surgery. The arrest, in a country where he thought he was safe from that sort of thing, came at the request of a Spanish court, where he stands accused of genocide, murder and torture of dozens of Spanish citizens.

How a former president will be tried for these crimes is a matter to be decided in Spain, but a world court, as envisioned during the month-long conference on the topic last summer in Rome, would provide many of the answers. The court, which would complement The Hague’s role of hearing cases against governments, would, under narrow circumstances, try individuals accused of genocide, war crimes and crimes against humanity. Notably, the United States was one of the few nations in Rome that did not reach agreement on this important issue.

If it proves justified, perhaps the trial of Gen. Pinochet will change the U.S. position.