ASHINGTON, Sept. 30 — A closely watched legal dispute over the ownership of works of art once looted by the Nazis reached the Supreme Court on Tuesday as the justices accepted an appeal by Austria and one of its state art museums on whether American courts have jurisdiction to resolve such cases.

An 87-year-old California woman, the niece and heir of a prominent art collector, Ferdinand Bloch-Bauer, who fled Vienna in 1938 and died shortly after the end of World War II, has spent decades trying to get back the remains of the collection he left behind. At issue are six paintings by Gustav Klimt, including two portraits of Mr. Bloch-Bauer's wife, Adele. The six paintings, now in the Austrian Gallery in Vienna, are worth more than $100 million.

Austria maintains that the paintings were left to the state and its museums under the will of Adele Bloch-Bauer, who died in 1925, and that the Nazis had illegitimate possession of them during the war does not change the fact that they properly belong to Austria now.

The niece, Maria V. Altmann, disputes that interpretation, maintaining that her aunt's preferences about the eventual disposition of the paintings never achieved the status of a formal bequest to the government. Ms. Altmann filed a lawsuit in Federal District Court in Los Angeles three years ago.

There has not yet been a trial to sort out the competing interpretations, and the Supreme Court will not decide the merits of the case. Rather, the question for the justices is whether the case can proceed at all under the Foreign Sovereign Immunities Act, a 27-year-old federal law that defines the terms for suing foreign governments in the federal courts. Although the issue is a technical one, it could be decisive in resolving a variety of cases involving the behavior of foreign governments and their agencies in World War II.

Such cases have been proliferating. In June, for example, the federal appeals court in New York reinstated a suit by Holocaust survivors and their heirs against the French national railroad, which transported tens of thousands of Jews and others to the Nazi death camps. That decision was appealed to the Supreme Court last month. Also in June, the federal appeals court here dismissed a suit against Japan, brought on behalf of 15 women from other Asian countries who had been subjected to torture and sexual slavery in World War II.

The status of two paintings by another Austrian painter, Egon Schiele, remains in dispute in New York, where they were claimed by two American families after they were lent by an Austrian foundation to the Museum of Modern Art in 1997.

The Nazis are believed to have seized 600,000 important works of art, with 100,000 still missing.

The location of the Klimt paintings has not been in doubt. Only their ownership has been disputed since the late 1940's, when Ms. Altmann and the other heirs tried and failed to get export permits to take them out of Austria. Several years ago, the Austrian government returned $1 million worth of porcelain and Klimt drawings to the family, but refused to yield on the paintings.

Ms. Altmann, an Austrian native who settled in California after the war and became an American citizen, turned to the federal courts after learning that a suit in the Austrian courts, where filing fees are based on a percentage of the amount in controversy, would cost nearly $2 million.

The Foreign Sovereign Immunities Act provides exceptions to the general rule that foreign governments are immune from suit. One exception authorizes suits "in which rights in property taken in violation of international law are in issue" in connection with "commercial activity." The question for the Supreme Court is whether that exception, which became official United States policy in 1952 and was not codified until 1976, can be applied retroactively to conduct that took place before 1952. So the issue in this case, Republic of Austria v. Altmann, No. 03-13, obviously encompasses foreign governments' immunity from suit for the entire World War II era.

Both the Federal District Court in Los Angeles and the United States Court of Appeals for the Ninth Circuit, in San Francisco, refused Austria's request to dismiss the suit, both on retroactivity grounds and on other grounds that the justices chose not to review. The federal government entered the case late in the lower court proceedings, unsuccessfully urging the Ninth Circuit to reconsider letting the case proceed.

Solicitor General Theodore B. Olson has not yet filed a brief presenting the government's views to the Supreme Court, but undoubtedly will do so now that the justices have accepted the case. The federal government's general position is that diplomacy, not litigation, should be used to resolve disputes growing out of the Holocaust.