SO OFTEN contemporary terror is international, the product not of one lone avenger but of a conspiracy sustained by people of different interests in different countries. That makes it all the more difficult to get to the bottom of the case, even when the actual gunman or bomber is found. It is not just that the facts are hard to establish; their political implications may be very hard to stomach. That is why one comes across such anomalies as the pope's reception last September of PLO chairman Yasser Arafat, whose organization evidently sponsored the very school for terrorists where John Paul's would-be assassin trained. Earlier, the French had allowed the Palestinian planner of the Munich Olympics massacre to leave France before going through the motions of trying to pick him up.

But look now at what is happening in Italy, the model among Western nations for legal correctness and political courage in this matter. In a number of cases -- the pope's would-be assassin, the Red Brigades people, who kidnapped U.S. Brig. Gen. James L. Dozier, and others -- the Italian authorities, ignoring the personal danger, have brought suspects to justice. Now they are looking into the foreign connections of some of these terrorists. The Bulgarian connection is under especially close scrutiny, not least because of the Bulgarians' reputation for service at the direction of Moscow.

Already the Italian police had established that the Turk who shot the pope had earlier killed a Turkish editor and then taken sanctuary in Bulgaria, and that in Sofia he had arranged the contacts that led to the cash, passport and pistol used in the attempt on the pope. A Bulgarian who works in his country's airline office in Rome has now been arrested on suspicion of complicity in that attempt. An Italian trade union aide jailed on spying and terrorism charges has reportedly acknowledged contacts with Bulgarian officials; this led a magistrate to confiscate the airline office's books. Two Red Brigades members implicated in the Dozier kidnapping have testified that the Bulgarians sought to provide help in that affair. The Bulgarians are screaming and, meanwhile, have picked up a couple of Italian tourists on fake spy charges, apparently for a later exchange.

The Italians are not boasting of their policy. But what they are doing -- arresting suspects and subjecting them to rigorous but fair trials, naming foreign names and accepting the international complications -- is uncommon and difficult and brave.