The demand for their return is decades old, of course, but the Olympic Games offered the perfect occasion for a new restitution campaign. Ever hopeful, Greece announced plans to build a new Acropolis museum to house the returned works. Amid growing British sympathy for the Greek claim, a British lobby called Marbles Reunited even tried a touch of subornment: a long-term loan of the sculptures, it said, would help London's bid to play host to the 2012 Olympic Games..

In other words, no.

"The range of the British Museum's collection is truly worldwide," Neil MacGregor, the museum's director, said recently. "They provide a uniquely rich setting for the Parthenon sculptures as an important chapter in the story of human achievement. It is this story which the British Museum exists to tell."

And yet restitution is not a subject easily dismissed. It has been made more topical by the recent - tardy - campaign to trace and return art looted from Jewish families by the Nazis in Germany and occupied countries. And it was again in the news last year after the sacking of the Baghdad Museum raised fears that stolen treasures would be smuggled out of Iraq and - not for the first time - find their way into private collections and museums in the West.

As it happens, the British Museum took a lead in demanding action to prevent looted works from leaving Iraq and in offering scientific help to the battered Baghdad Museum. But with its treasure house of ancient and primitive art from all over the world, the British Museum is itself uniquely vulnerable to claims, not only on the order of the Elgin marbles and the Rosetta stone (demanded by Egypt), but also of less spectacular objects of importance to their cultures of origin.

Indeed, an object once considered of minor worth can assume enormous symbolic weight 150 years later. So it is with the most recent case to embarrass the British Museum involving aboriginal bark etchings. When they were brought to Britain in the mid-19th-century, Australia's native inhabitants were a repressed minority with virtually no rights. Today, with their art widely appreciated, they are better organized to defend their interests.

Last month, the Dja Dja Wurrung Native Title Group of Western Australia obtained an emergency declaration order to block the return of two bark etchings and a carved wooden emu loaned by Britain for a show at the Museum Victoria in Melbourne. One bark etching and the carving came from the British Museum; the other etching came from the Royal Botanical Gardens in Kew, outside London.

"They belong in Australia," Gary Murray, secretary to the Dja Dja Wurrung group, told The Times of London. "If we had your crown jewels, you'd be knocking our doors down."

The British Museum and Kew Gardens were not happy. In a joint statement, they pointed to an Australian government certificate authorizing the objects' return and noted that Western museums would not lend works if they were in danger of being seized. "The Emergency Declaration puts at risk the very legal framework that allows such exhibitions to take place," they warned. For the moment, the dispute is being handled by the Museum Victoria.

But while museums need a legal framework to protect their works on loan, the aborigines also have a point. The bark etchings are hardly central to the British Museum's collections but, as the earliest surviving examples of the art, they can help the aborigines to rebuild their shattered history and consolidate their identity. And the same applies to other works of spiritual importance that have occasionally been returned to native peoples.

Last year, the Manchester Museum in Britain returned four aboriginal skulls and two limb bones to Australia. In 2000, France repatriated the body of an unfortunate South African woman, known as the Hottentot Venus, which had been displayed in the Musée de l'Homme in Paris since the early 19th century. In 1998, the Glasgow Museum returned the so-called Ghost Dance Shirt to the Lakota Sioux tribe in South Dakota.

Where should the line be drawn? No one denies that European and American archaeologists, explorers, collectors and scholars have played a key role in finding, studying and preserving Egyptian, Assyrian, Greek, Roman and pre-Columbian treasures. No less true, examples of 19th-century tribal art from Africa and Oceania survive today because they were first collected by outsiders. And if all were returned to their countries of origin, Western museums would be emptied.

A 1970 Unesco convention prohibited the illicit import, export and transfer of cultural goods, but it set no rules for restitution. The 1995 Unidroit Convention on stolen or illegally exported cultural objects contemplated restitution, but it has been ratified by few countries. Thus, in 1997, when a Paris museum discovered that three newly acquired pre-Islamic Nok statues had been pilfered from Nigeria, France was under no legal obligation to return them. Instead, acknowledging a moral duty, it donated them to Nigeria, which then lent them to France for 25 years.

But even with older acquisitions, it seems valid to ask: where once conquered or colonized countries now see their prized treasures in Western museums, do these countries or do the museums own the works? Take, for instance, the stunning 16th-century metal sculptures known as the Benin Bronzes. They were seized by British forces in a punitive raid in 1897. Some are in the British Museum, others elsewhere. Nigeria has asked for their return - so far in vain.

At least the Elgin marbles were not war booty. The British Museum says Elgin had Turkish permission to remove them, while Greece says Elgin obtained them through bribery. But that is no longer the issue. A more persuasive Greek argument is that the marbles should be reunited with other surviving Parthenon sculptures in Athens so that people could understand the context in which they were created. And to circumvent the ownership debate, Greece proposes a long-term loan.

But the British Museum sees a long-term loan as a euphemism for a hand-over. It notes that the Parthenon sculptures are not properly displayed. It believes its own sculptures would still be at risk in Athens. And it reiterates their place in the museum's universal story. So there we are. The British Museum is not about to part with the Elgin marbles. And, as plainly, the Greek campaign to recover them will not end with closing ceremony of the Olympic Games on Aug. 29.

Alan Riding can be reached at pagetwo@iht.com