Hundreds of ethnic Albanians in Kosovo arrested for serious crimes, including murder, assault and rape, have been set free without an indictment or trial because the province still lacks a functioning criminal justice system six months after NATO forces arrived, according to United Nations documents.

In many cases, the suspects are quietly let go within two to three days of their detention by the few judges serving here, the documents show. More than 40 percent of all those arrested are released, according to one study.

In addition, a number of other suspects have been held by NATO forces for nearly six months without an indictment or trial, making them eligible for release shortly under European and Yugoslav laws proscribing long-term detentions. Under these laws, the first murder suspect eligible for release cannot be legally detained past Wednesday; the United Nations is scrambling to find a way to keep him and others behind bars.

Once released, police say the likelihood these alleged criminals will return to custody and face a trial is slim. Although many of the victims were Serbs--and the crimes were evidently inspired by atrocities Yugoslav forces committed before and during the war here this spring--an even larger number of victims are ethnic Albanians who now lack any legal recourse and may be inspired to commit acts of revenge to settle scores, U.N. officials here say.

"Anywhere else in the world, people who throw grenades would spend some time in jail," said one official of the nascent U.N. police force, who asked not to be named.

In the nearly six months since NATO forces arrived, only 24 of the hundreds of people arrested here have had a hearing or courtroom trial--and in only one city, Prizren. Elsewhere in Kosovo, no judges have been appointed to fill as many as 350 vacant slots.

None of the court facilities have even rudimentary supplies, although the Organization for Security and Cooperation in Europe (OSCE) has recently budgeted $80,000 in U.S.-donated funds for such essentials as window glass, paper, pens and filing cabinets.

More importantly, however, international administrators have yet to agree on what legal code should be enforced, effectively stymieing any judicial progress.

Bernard Kouchner, the top U.N. administrator in Kosovo, inherited a hastily drafted regulation signed by his predecessor shortly after NATO forces arrived in mid-June that makes the Yugoslav criminal code the law of Kosovo. Kosovo is a province of Serbia, Yugoslavia's dominant republic. But ethnic Albanian judges and lawyers have unanimously refused to implement the Yugoslav law, because it differs from a preferred criminal code that had been in force prior to 1989 when Kosovo was autonomous and ethnic Albanians had political control.

"No Albanian will apply Yugoslav law," said Blerim Reka, an ethnic Albanian who chairs a U.N. advisory group on the judicial system. "If we apply the Serb criminal code, we will be against our own will for independence" from Yugoslavia.

Faced with a universal boycott by ethnic Albanians, who now make up 95 percent of the population, Kouchner privately proposed two months ago to embrace the pre-1989 code.

But U.N. officials in New York, seeking to strengthen Yugoslav sovereignty over Kosovo, have been slow to approve the change, according to a U.N. official here.

"This applicable law issue has been a very serious complication . . . in the administration of justice," said Daan Everts, the top OSCE official in Kosovo. "The time taken to resolve this has been painfully long." Everts called the establishment of a functioning court system "the most important issue" in Kosovo in the months since Yugoslav forces withdrew from the province to halt NATO's bombing campaign.

According to other officials, the United States had strongly backed the shift to another legal code, and after 6 months, only Russia dissents from this view. "It's a hot, emotional, political issue that's hard for the international community to deal with," an official here said. "The chemistry in New York is different than the chemistry on the ground here," a second official here said.

Meanwhile, Western officials are concerned that the 55 appointed ethnic Albanian judges are being pressured or corrupted into treating accused ethnic Albanians better than Serbs. The only seven Serb judges in Kosovo resigned after one was threatened with murder.

For example, police officials said that in the city of Prizren, four ethnic Albanian men employed by the provisional ethnic Albanian government were arrested for attempting to extort $6,000. But a local judge set them free two weeks ago without any explanation, and the victim subsequently recanted his accusations.

"Nobody is willing to give us information, because they are afraid; they feel pressure" caused in part by the absence of any credible criminal penalties in Kosovo, a Prizren police official said.

The judges have each been paid $450 since the war ended, leaving ample opportunity for others to supplement their salaries if desired--although no cases of corruption have been proven. Police, the OSCE, and the Lawyers Committee for Human Rights have called for the appointment of international jurists and prosecutors. But U.N. officials said the idea has not been seriously considered.