PARIS — Paris. -- There are two principles which must be established in the Yugoslav crisis. The democratic world will have to live with the precedents set there for years to come.
The first principle is that among civilized countries frontiers are not to be changed by military aggression. The second is that the security and human rights of national minorities are of international concern and will be defended by the community of democratic nations. The first warning is addressed to Serbia; the second to Croatia.
These steps are essential if there is to be a peaceful transition in what now is the Soviet Union, as well as in the Balkans. The U.S.S.R. and the former communist dictatorships of Eastern Europe are desperately concerned to become integrated into the free and prosperous community of European democracies. There is a code of conduct for membership. No concessions can be made to military aggression, or to invidious discrimination or aggression against national minorities.
Threatened minorities and challengeable frontiers exist everywhere in what used to be the communist world. There are more of them in the Soviet Union than during tsarist days because it was Stalin's deliberate policy to transport whole peoples from their place of origin, installing them in the midst of another and potentially hostile group in order to better control both.
The entire region was formed by successive migrations, since prehistory, of the central Asian peoples westward into Europe. Individual groups halted, settled, were bypassed by others, or displaced, or surrounded, most eventually finding their political identity in the loose imperial systems that grew up around the state of Muscovy in Russia or in the Byzantine Empire, successor to Rome, or Byzantium's own successor, the Ottoman Empire.
In the western regions their tribal kingdoms became primitive monarchies, in one way or another eventually absorbed into the western dynastic system, notably into what became the Austro-Hungarian Dual Monarchy.
But as these loose and fundamentally feudal empires broke down in the 19th century, individual nationalities set out to make themselves nation-states on the modern western model, and to become as large and powerful as possible.
Slobodan Milosevic and the leaders of Yugoslavia' Serbian-dominated Yugoslav Army are still at it. There are others elsewhere in this region who still see the world in equivalent terms -- which elsewhere have been discredited by the First and Second World Wars, and by eight decades of the totalitarian experience.
The Yugoslav crisis is the product, first, of Serbia's attempt to create a ''Greater Serbia'' by annexing those portions of modern Croatia populated by a Serbian minority, and by establishing a dictatorship over what now is the ostensibly autonomous Yugoslav region of Kosovo, once populated by the Orthodox Christian Serbs and a center of their civilization, but in modern times overwhelmingly Muslim in religion and Albanian in ethnic composition.
The crisis is also the result of the gross atrocities committed just 50 years ago by Croatians against the Serbs. Fascist Italy and later Nazi Germany sponsored a fascist Croatian autonomy movement in prewar Yugoslavia, the Ustasha, which between 1941 and 1945 became a fascist Croatian state and conducted the cold-blooded slaughter of tens of thousands of Serbs. No one in Serbia has forgotten this.
The European Community's ''peace'' conference (where is the peace?) which was to open over the weekend in The Hague under Dutch presidency and Britain's Lord Carrington's direction, emphasizes the protection of national minorities in Yugoslavia.
This is essential. The claims of minorities are to arbitrated by a commission composed of the presidents of the constitutional courts of five of the European Community's member-states. The eminence and disinterestedness of this body is beyond question.
The fundamental challenge to the conference, however, is to obtain a cease-fire. Serbia and the federal army appear determined to continue their offensive until they have conquered what they want from Croatia. They expect then to negotiate from the basis of a military fait accompli.
The international community must insist that the territorial gains of Serbia in this war will not be recognized, and that if Serbia holds to its present course it will be made the object of both European Community and United Nations economic and diplomatic reprisals.
Serbia in this case will have put itself in exactly the position of Saddam Hussein in August 1990 (who also had certain legitimate claims to make against the country he invaded).
As President Bush is unlikely to collect another war-making coalition in order to defend Croatia, the international community will have the opportunity to find out what economic and political sanctions can in fact accomplish.