On May 22, Yugoslav President Slobodan Milosevic became the first sitting head of state in history to be indicted by an international tribunal when he was charged with committing war crimes and crimes against humanity in Kosovo. The indictment--which does not charge him with genocide--was accompanied by an international arrest warrant for Milosevic. Yet more than four months later, there is no sign of any real effort to bring him to trial. And no one should expect that Milosevic will be tried any time soon--if ever.

The International Criminal Tribunal for the Former Yugoslavia has no constabulary, and that is its inherent weakness. Created by the U.N. Security Council in 1993, it must rely on the voluntary cooperation of the world's nations, including the very governments whose officials it seeks to prosecute. In the absence of the cooperation of the governments of Bosnia, Croatia and Serbia, the tribunal has had to depend on a divided Security Council and a reluctant NATO to enforce its orders.

As a result, Milosevic remains president of Yugoslavia. He continues to command a massive police and paramilitary network that represses opposition. He still runs the state television and radio stations that continue to barrage the Serbian people with ethnic nationalist propaganda. And he controls the third-largest army in Europe, which poses a continuing threat to Vojvodina and Sandzak--enclaves in Serbia populated mostly by non-Serb ethnic groups--as well as to Montenegro, the other Yugoslav republic, and to neighboring Macedonia and Bosnia.

The principle behind the prosecution of leaders before an international tribunal is that it discourages collective guilt and promotes national reconciliation. Because Milosevic and other indicted Serb leaders have not been tried, these goals have been frustrated.

Yet the United States and other members of the Security Council have shown no interest in doing what's necessary to bring Milosevic to trial. In early June, the Security Council adopted a peace plan to end the Kosovo war that did not give NATO forces in Kosovo a mandate to arrest indicted war criminals. And even if the NATO troops had such powers, the peace agreement would prohibit them from crossing the border into the rest of Serbia, where Milosevic and company presumably still reside. At the same time, the council rejected a provision that would have triggered economic sanctions against Serbia if it failed to comply with the Milosevic arrest order. And it refused to require countries to freeze the assets of indicted Yugoslav war criminals.

A week earlier, the war crimes tribunal, in an ambitious but questionable interpretation of its powers, had ordered all countries to freeze Milosevic's assets, most of which are in foreign banks. As far as I know, no country where he has accounts has complied.

Several Western leaders have threatened that billions of dollars in postwar economic assistance to Serbia will be withheld until Milosevic is removed from power. But, most revealing of all, they have not made his surrender to the international tribunal part of the bargain. As a result, some Serbia experts have concluded that Milosevic was at least implicitly promised some type of immunity from prosecution in return for his agreement to the Kosovo peace plan.

As a former adviser for U.N. affairs at the State Department, where I was responsible for war crimes issues, it is clear to me that Milosevic must be arrested and prosecuted. Being satisfied with his ouster alone would be an extraordinarily shortsighted foreign policy goal. Even if Milosevic ultimately agrees to relinquish his official position under pressure from the West--the chances of his being overthrown are slim, despite ongoing protests--he is likely to remain a threat much like Radovan Karadzic. Karadzic, the former president of the Bosnian Serbs who was indicted as a war criminal but never arrested, continues to plague the Bosnian peace effort.

In hindsight, it is easy to see that the prospects for peace in Bosnia would have been far greater if Karadzic had been apprehended and prosecuted, rather than simply banished from office.

The lesson of Karadzic's non-prosecution is that indictments alone are meaningless if there is no real prospect of trial and punishment. The apprehension and trial of Milosevic, the person most responsible for atrocities in both Kosovo and Bosnia, is critical to achieving lasting peace in the Balkans. As long as he remains at large, NATO forces will have no choice but to remain in Bosnia and Kosovo to enforce an unstable peace; if they withdraw, war will return.

The failure to arrest Milosevic and to punish Serbia and other countries that refuse to cooperate with the tribunal have undermined the credibility of NATO and the Security Council. Moreover, the failure has eroded any deterrent value the tribunal might have had not only in the Balkans but around the world. The lasting contribution of the court is also in jeopardy. As Richard Goldstone, the tribunal's first chief prosecutor, told me while I was writing a book on the subject, "If this situation [non-arrest of the major Yugoslav war criminals] is not corrected, the establishment of the Yugoslav tribunal will have caused more harm than good."

And unlike the Nuremberg tribunal that tried the Nazi elite following World War II, the Yugoslav tribunal has tried mostly foot soldiers and members of paramilitary groups. This sends the perverse signal that the tribunal will prosecute only the minor figures who fall into its hands, surrender or are easily captured by NATO troops, while the leaders most responsible for the atrocities enjoy de facto impunity.

From the beginning, the Security Council's motives in creating the tribunal were questionable. During the negotiations to establish the court--talks in which I participated on behalf of the U.S. government--it became clear that several of the Security Council's permanent members considered the tribunal a potential impediment to a negotiated peace settlement. Russia, in particular, worked behind the scenes to try to ensure that the tribunal would be no more than a Potemkin court.

The United States's motives were also less than pure. America's chief Balkans negotiator at the time, Richard Holbrooke, has acknowledged that the tribunal was widely perceived within the government as little more than a public relations device and as a potentially useful policy tool. The thinking in Washington was that even if only low-level perpetrators in the Balkans were tried, the tribunal's existence and its indictments would deflect criticism that the major powers did not do enough to halt the bloodshed there. Indictments also would serve to isolate offending leaders diplomatically, strengthen the hand of their domestic rivals and fortify the international political will to employ economic sanctions or use force. Indeed, while the United States and Britain initially thought an indictment of Milosevic might interfere with the prospects of peace, it later became a useful tool in their efforts to demonize the Serbian leader and maintain public support for NATO's bombing campaign against Serbia, which was still underway when the indictment was handed down.

Thus, it is hardly surprising that the Security Council has not imposed sanctions on countries that refuse to comply with the tribunal. Nor is it surprising that the Security Council gave the NATO force in Bosnia the authorization, but not the responsibility, for apprehending indicted war criminals. Indeed, no attempt has been made to arrest Karadzic, although he has passed through NATO checkpoints in Bosnia and has appeared publicly in areas controlled by NATO on several occasions.

Serbia's noncooperation with the tribunal dates to 1996, when it decided not to arrest Serbs who had been indicted for war crimes in Bosnia. The Security Council's refusal to impose sanctions on Serbia's lack of cooperation, as well as the failure of NATO troops to apprehend Karadzic, undoubtedly emboldened Milosevic to pursue his policy of ethnic cleansing in Kosovo with the expectation that he, too, would never have to account for his actions. The failure to arrest Milosevic, in turn, could very well have sent the same signal to the military leaders thought to have committed crimes against humanity in East Timor and elsewhere. Thus, we may have won the Kosovo conflict, but because of our anemic policy on indicted war criminals, we are losing the war against impunity.

Michael Scharf is a professor of law and director of the Center for International Law and Policy at the New England School of Law in Boston. He is the author of "Balkan Justice" (Carolina Academic Press).