THE KREMLIN has finally moved to silence and perhaps also to exile. Andrei Sakharov, at once one of the Soviet Union's premier scientists and its most respected and outspoken dissident. The event is no less outrageous for having been predictable. Mr. Sakharov had earned two world-class reputations -- as a servant of the state in physics and as a challenger of the state in human rights -- even before Jimmy Carter expressed a direct personal interest in his welfare early in 1977. That embrace in effect made the Nobel peace laureates' status as an active opposition figure a hostage to President Carter's standing with the Kremlin. When the Kremlin turned on Mr. Carter, on account of the president's stern reaction ot its aggression in Afghanistan, Mr. Sakharov's days were numbered.

It is hard to exaggerate the importance of the role occupied by Mr. Sakharov. He has represented the valiant Soviet Minority that believes that the achievement of peace and progress for the Soviet Union requires both detente and a degree of democratization. With splendid personal courage and perseverance, he has spread this point of view through his international published writings and his contacts with foreigners in Moscow. His world reputation gave him a measure of protection, as did the influence of Kremlin "doves" who found his dissidence useful to their own political designs. Moreover, much of the international scientific community was ready to condition its official cooperation with Moscow on Mr. Sakharov's personal status. It now goes without saying that by silencing him the Kremlin has chosen to put a good deal of that cooperation in jeopardy.

For all the immediate political implications of Mr. Sakharov's fate, it is useful to step back a pace and ask a basic question: what kind of country is it that denies a natural place and a decent life and ultimately the right of residence to patriotic citizens who are, by any reasonable standard, adornments to their society? People like Andrei Sakharov and Alexander Solzhenitsyn, not to speak of hundreds, thousands of lesser-known victims of political persecution and exile, would be and are recognized as outstanding individuals in many other lands. In their own land they are officially reviled. It is tragic for the, and for their countrymen.