A YEAR AGO in Brighton, England, terrorists bombed a hotel in which Prime Minister Margaret Thatcher was staying. She was not injured, but six people were killed and dozens wounded. If some of the criminals involved in that bombing turned up in, say, Seattle, would you not expect the United States to return them to Britain for trial? Given this country's strong and recently expressed beliefs about bringing terrorists to justice you may think that extradition would be a foregone conclusion, especially since the country requesting it is one with which Americans share values and a common tradition of justice. But that is not the case.

The current extradition treaty with Great Britain provides that the United States will not return persons charged with or convicted of "political" offenses, a category that quite likely would include an attempt on the prime minister's life. In a number of recent cases, in fact, American courts have refused to extradite persons charged with crimes in connection with the continuing violence in Northern Ireland. At least one is an escaped convicted murderer, but a New York judge held that since he had killed a British soldier his offense was a political one and he was not subject to extradition.

To provide a foundation for proceeding against terrorists now enjoying sanctuary in the United States, the American and British governments agreed last spring to amend the treaty and limit the exception for political offenses. It would be unavailable in cases involving violence, hijacking and sabotage, hostage-taking and certain offenses involving firearms, explosives and damage to property. The amendments must be ratified by the Senate, but after three hearings by the Foreign Relations Committee -- and a lobbying campaign by supporters of the IRA in this country -- action on the proposal has been postponed. That is disgraceful.

For at least three years Congress has been grappling with legislation to amend the extradition law and set guidelines for the courts to determine which offenses are political. Nothing has been enacted. Some legislators believe that a single standard must be applicable to all countries, but that makes no sense. It is reasonable to differentiate between assaults against totalitarian governments and acts designed to overthrow a democratic government where there are alternatives to violence. There are valid reasons for refusing to send an accused back to a trial by a kangaroo court, but they do not apply in countries with an independent and fair judiciary. There is nothing inherently wrong with making different agreements with different countries.

The Senate's failure to ratify the treaty amendments not only affronts this country's relationship with a primary ally. Worse, it undermines the American position on all countries' responsibility to bring suspected terrorists to justice.