A U.S. charitable foundation said Wednesday that it was the anonymous bidder which paid $530,000 for 24 Native American masks, and will return them to the Hopi Nation in Arizona and the San Carlos Apache tribe.

"These are not trophies to have on one's mantel," said Gregory Annenberg Weingarten, director of the Los Angeles-based Annenberg Foundation. He added: "They do not belong in auction houses or private collections."

Twenty-one masks are being returned to the Hopis and three to the San Carlos Apaches.

They were auctioned off despite actions by the U.S. Embassy, which had made a request for delay on behalf of the Hopi and San Carlos Apache tribes, to allow them time to come to France and identify the artifacts and investigate whether they have a claim to the items under the 1970 UNESCO Convention on the Export and Transfer of Ownership of Cultural Property. Both France and the U.S. are signatories to the treaty.

It was a happy ending for the Hopi tribe following a series of legal setbacks in efforts to delay the sale of the masks, arguing that they represent ancestral spirits and shouldn't be sold. The tribe has said it believes the masks, which date from the late 19th and early 20th century, were taken illegally from a northern Arizona reservation in the early 20th century.

"Our hope is that this act sets an example for others that items of significant cultural and religious value can only be properly cared for by those vested with the proper knowledge and responsibility. They simply cannot be put up for sale," Sam Tenakhongva, a Hopi cultural leader, said in a statement Wednesday.

The Katsinam masks look like surreal faces made from wood, leather, horse hair and feathers and are painted in vivid pigments of red, blue, yellow and orange. Unlike commercial art, the Hopis argue, these objects are akin to tombs and represent their ancestors' spirits, nurtured and fed as if they are the living dead.

Pierre Servan-Schreiber, a lawyer who represents the Hopis, told The Associated Press that he'd personally bought one mask to return to the tribe.

In a similar dispute in April, a Paris court ruled that such sales are legal, and around 70 Hopi masks were sold for some $1.2 million, despite protests and criticism from the U.S. government and actor Robert Redford.