IT'S UNDERSTANDABLE that many citizens are angry and fearful, or deeply troubled, that Hamaas Khaalis and three of his 11 fellow terrorists went "free" after releasing their hostages. The impression thus cast was that the community was endangered and the gunmen were rewarded. Some citizens - and some law enforcement authorities - insist that a promise of release made, under duress, to a terrorist need not and should not be kept; this view is expressed in several appearing elsewhere on this page today.

We take another view. We point out first that the four did not exactly go "free." Promised release without bail pending grand jury action, Mr. Khaalis got the special favor of a 5 a.m. hearing but then went to his 16th Street home virtually under house arrest. Given the bail act's requirement that a previously "clean" suspect be freed unless he's likely to flee, he might have won release even if it hadn't been promised to him. The other three released men, similarly rooted in the community, were the three at the Islamic Center, where the hostages, except for being held, were not harmed. There is an argument, which we ourselves have made and would make again here and now, for amending the bail act to provide judges and more latitude to detain suspects considered to be dangerous. But the law, whatever it is, must be observed.

Consider that the terrorists, felony murder suspects all, were not promised their first demand, the handing over of the men sentenced for killing the Hanafi family in 1973. Not were they promised amnesty or escape for themselves. Thus was the essential sanctity of the criminal justice system honored - the crucial consideration, after the saving of human life, in our view. During the siege, they won suspension of the movie "Mohammad, Messenger of God." But evidently this was done not so much by official promise as by community cooperation. That showings of the film quickly resumed elsewhere may turn out to have been unwise but cannot fairly be laid to a breach by the police who negotiated the end of the siege.

If this were to be the last act of terrorism, then one could safely break the promise of conditional release given Mr. Khaalis. But it will not be the last act. There may be no such thing as a last act. Each act is a precursor to the next. This unhappy fact forces the authorities to consider what precedents and expectations they are bequeathing to the next set of actors. And this in turn forces each society to contemplate its own peril, its own temper, its own cohesiveness, its own disposition to regard hostages either as unlucky individuals or as representatives of the society as a whole.

In America, we suggest, to break a promise is to risk inclining the next terrorist to hold out rather than to bargain. This is the Attorney General's position. We support it. We recognize, however, that it generates its own dilemma. A terrorist inclined to think the authorities will keep their words may thus be emboldened to commit an act which uncertainty might have deterred. One cannot be sure.

The answer, if there is one, is to promise as little as possible and then to deliver as much as possible. This seems to us just what the Washington police did. They gave away nothing important. In particular, they ensured that all the terrorists remain within reach of the law. They saved lives. The next terrorist incident may present harder choices. This one, we believe, was handled with a deft sense of the operational contingencies and of the human and social priorities involved.