THE HAGUE, Feb. 12 — Belgium's highest court said today in Brussels that Prime Minister Ariel Sharon of Israel could be tried for war crimes under the nation's laws, but not as long as he enjoyed the immunity of his office.

The ruling, while blocking the case against Mr. Sharon, did allow a Belgian court to hear the case against Mr. Sharon's co-defendant, Amos Yaron, the former Israeli Army chief of staff.

In its summary, the high court said investigations and a trial could proceed even if a suspect was not physically present in Belgium. Several cases involving foreign leaders, past and present, had been on hold for almost a year, pending the high court's decision.

The case against Mr. Sharon and Mr. Yaron dates back to 2001, when survivors of the 1982 massacres at the Sabra and Shatila refugee camps in Beirut filed a criminal complaint, holding the two Israelis responsible for the deaths of their relatives. Christian militias, backed by Israel, did the killing, but an Israeli commission of inquiry in 1983 concluded that Mr. Sharon, then the defense minister, had a personal responsibility for the events.

By filing their case in Belgium, the survivors hoped to make use of the country's 1993 law that allows the courts "universal jurisdiction" over crimes against humanity or war crimes anywhere.

Many states have given their courts universal jurisdiction over some crimes. But until now, Belgium's so-called antiatrocity law went further by barring immunity claims and by allowing the courts to investigate crimes committed anywhere, regardless of the nationality of the victims or the perpetrators.

Today's ruling recognized the immunity of high public office, like the posts of prime minister, president and foreign minister. But the judges implied that the case against Mr. Sharon could be pursued after he left office, lawyers said. Citing that ruling, Luc Walleyn, a lawyer for the plaintiffs, hailed the decision as a victory.

Daniel Shek, the Israeli Foreign Ministry's director of European Affairs, described the decision as "very problematic," according to Reuters.

The Israeli case is one of many pending in Belgium involving charges of grave human rights violations. Lawyers handling the cases said they were elated with today's ruling, because it overturned a decision last year in a lower court that held that an accused person had to be present in Belgium to be investigated.

"This was a big breakthrough, a big step forward," said Georges-Henri Beauthier, a human rights lawyer. "Cases had been blocked in several courts, awaiting the high court's ruling." Mr. Beauthier said he could now continue pursuing the case against Hissène Habré, the former ruler of Chad, who lives in exile in Senegal. Today's decision effectively means that prosecutors can issue international arrest warrants and apply for a suspect's extradition, he said.

Belgium's antiatrocity law has made the country into a magnet for grave human rights violations, and cases against two dozen current or past leaders are still pending in Belgian courts.

Critics in Belgium have attacked the law, arguing that Belgium could not become the "world's court." Several legislators have said they want Parliament to "reinterpret" the law.

But changes appear unlikely soon. Now that the high court has ruled, the Belgium's prime minister, Guy Verhofstadt, said today that there was no need for Parliament to intervene.