THE ASSASSINATION of Ali Akbar Tabatabai in Bethesda was, unfortunately, part of a wider pattern. The man suspected of pulling the trigger was evidently connected to Iran's diplomatic mission here in Washington. The resonance of the Letelier killing is not the only thing to notice here. From North Africa to the Persian Gulf is a region of insecure governments, and several of them have turned to the gun to rid themselves of their expatriate opponents. It has been going on for some time. But, relying on oil to deflect any political consequences, these governments have been running their terrorist campaigns increasingly openly out of their embassies in Europe and, perhaps, Washington.

As in the matter of aircraft hijacking, it's almost impossible to control this kind of terrorism unless all countries are prepared to enforce a prohibition together. Two years ago a former prime minister of Iraq was shot dead at the entrance of a London hotel. The British government prompty expelled 11 Iraqis, including seven diplomats. That's an effective response.

France, in contrast, has deluded itself into thinking that it can gain political advantages among the Arabs by ignoring the gunplay originating in certain Middle Eastern embassies in Paris. The French position has been notorious ever since 1977, when the government allowed Abu Daoud to walk out of the hands of the police and onto an airplane leaving the country. He has been implicated in a number of terrorist strikes, including the murder of the Israeli athletes at the 1972 Munich Olympics. The only good thing is be said about French complaisance is that it has brought France no profit whatever -- nothing but a series of killings in French streets.

Two years ago in Paris an affray broke out in the Iraqi Embassy, which turned out to contain a remarkable armory of powerful weapons. In the midst of this affair, an Iraqi guard shot and killed a French policeman. The French government apparently did nothing.

Last December, a nephew of the former shah of Iran was assassinated in Paris. This month five men tried to kill Shahpour Bakhtiar, the last premier of Iran under the shah's rule. Mr. Bakhtiar was not hurt, but one of his neighbors and, again, a French policeman were killed. On the same day, the Paris office of Iran Air was bombed -- presumably by the other side in the Iranian quarrel. Last week a former premier of Syria, Salah Eddin Bitar, was very professionally killed at his office in Paris.

The trouble isn't limited to France. Since mid-March, at least eight critics of the Qaddafi regime in Libya have been murdered -- four in Rome, others in London, Bonn and Athens. The incidence of these cases is accelerating.

Here in Washington, the 1973 murder of an Israeli military attache remains unsolved. More recently, several diplomats at the Libyan Enbassy were threatening and harassing the alleged enemies of Col. Qaddafi. When the United States moved to expel them, the Libyan government hinted at an oil embargo. It might be noted, incidentally, that the diplomats shortly departed but the flow of oil continues.

Now the investigation of the Tabatabai murder appears to lead in a straight line to the Iranian Interests Section of the Algerian Embassy here. If that link is established, the United States will have no alternative to closing down that Iranian mission and throwing out everyone connected with it. To temporize merely invites further political violence, as the French example painfully demonstrates.