PARIS. — Paris -- Slowly, too slowly, the great mutation occurs. The principle of absolute national sovereignty is being overturned. It has governed international life since early in the 19th Century, when the church's claim to an authority superior to that of the crown foundered in the collapse of the Holy Roman Empire and the rise of the secular nation-state.
The civil war in Yugoslavia has rendered this service to us. Coming just after the international mobilization to rescue Kuwait from Iraq's aggression, the wanton and futile Serbo-Croatian war has forced the European governments to confront the question of whether aggression and ethnic war can any longer be tolerated on a continent which has gone through what Europe experienced between 1914 and 1989.
They have not delivered an answer. At this moment, it looks very much as if there may shortly be a second Yugoslavian war. The effort to instigate one has already begun in the charming and tragic city of Sarajevo, in Bosnia-Herzegovina.
At this writing emotions there are feverish, and the political situation very fragile in the aftermath of Sunday's referendum favoring national independence. The majority of voters, mainly Muslims and Croatians, favored independence; the Serb minority is opposed.
I describe Yugoslavia as a European problem even though the United Nations currently has taken over the peace-maker's role, with Cyrus Vance's missions there in recent weeks, and the decision by the Security Council to send a peacekeeping force -- a decision which may have come too late.
I do so because the European continent's internal problems no longer are subject to superpower settlement. The Soviet Union, which silenced Balkan and East European internal conflict for a half-century, is finished. The United States no longer has the will to intervene in European affairs.
The current presidential campaign in the U.S. makes it plain where American preoccupations now lie. They scarcely reach to Yugoslavia. Yugoslavia is a matter of specialist concern in the U.S. today; the Serb and Croat ethnic communities in the nation's old industrial cities have dwindled in numbers and influence.
The Yugoslav affair -- and those like it which may come in the future -- will be dealt with either by the other European powers or by no one at all. The best that should be expected from the United States is support for European initiatives.
Ethnic and national conflict in the ex-Soviet Union will, for sound reasons, attract much greater American attention.
There is, however, little or nothing the United States can do about a war between Armenians and Azerbaijani over Nagorno-Karabakh. Things can be done about wars among the Yugoslav successor states. They are vulnerable, and in the center of Europe.
Even now, what was done to halt or block enlargement of the Serbo-Croat war was unprecedented.
It had nothing in common with the Iraq-Kuwait intervention, which conformed to the U.N.'s action in Korea in 1950. International aggression had taken place, the United Nations was mobilized under American leadership, the Security Council authorized an American-commanded military force to punish aggression and restore the victim-nation's integrity.
The League of Nation's economic sanctions against Italy in 1933, in retaliation for Italy's invasion of Ethiopia, were similar measures of international reprisal.
Uninvited international intervention into the internal affairs of a state is another matter entirely. Until now it has been held an unacceptable attack upon the principle of unlimited state sovereignty.
The Yugoslav crisis was produced by the secession from Yugoslavia of two component-states, Slovenia and Croatia, but international intervention and the dispatch of European Community observers preceded EC recognition of the two states' independence, which Serbia continues to contest in exactly the name of Yugoslav sovereignty.
These EC and U.N. actions have been in marked contrast to the conduct of the European powers during the last Balkan Wars, in 1912-13. Then, Serbian military expansion at the expense of Ottoman Turkey and Bulgaria was tolerated by the international community, contributing to the tensions that exploded into world war when the Austrian archduke was assassinated by a Serbian terrorist in 1914.
Today's international intervention, tentative as it has been, marks a step forward in the democracies' assumption of collective responsibility for peace and human rights within the areas they can reasonably expect to influence, and which are of the greatest concern to them.
The Helsinki Final Act of 1975, with its seemingly innocuous guarantees of human rights, and the intrusive ''process'' that followed to support those guarantees, proved an extremely important initiative in this respect, and had a powerful liberalizing influence inside the Communist bloc.
Now the European Community and the United Nations are ''interfering'' in Yugoslavia's national disintegration. What they have thus far done has been improvisation, and not particularly successful, but it is a start on something new.
We now are in a situation where improvisation and experiment are essential, in contrast to the big programmatic reforms of 1918 and 1945, the League of Nations and United Nations.
Both those had their limited successes, but both rested on flawed assumptions and possessed the fundamental handicap of universal membership. The ''world community'' does not exist.
A democratic community does exist. So does a North Atlantic Community. So does the European Community. All are based on common value commitments.
It is from them that constructive reform now must come.
William Pfaff is a syndicated columnist.