PARIS (AP) ― A U.S. charitable foundation said Wednesday that it was the anonymous bidder that paid $530,000 for 24 Native American masks in a contested Paris auction two days ago, and will return them to the Hopi and the San Carlos Apache tribes.

“These are not trophies to have on one’s mantel,” said Gregory Annenberg Weingarten, director of the Los Angeles-based Annenberg Foundation, which revealed itself to be the secret caller that triggered a bidding war in Monday’s highly publicized auction.

He added: “They do not belong in auction houses or private collections.”

Twenty-one vividly colored masks made of leather, horsehair, wood and feathers bought at Drouot auction house will be returned by the foundation to the Hopis and three hood masks to the San Carlos Apaches.

It was a happy ending, at least in one chapter in the Hopi tribe’s battle to regain its tribal patrimony, following a series of legal setbacks in efforts to delay the sale of the masks last week, 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.

The U.S. Embassy had also called for a delay so that tribal representatives could come to France to identify the artifacts and investigate whether they have a claim under the 1970 UNESCO Convention on the Export and Transfer of Ownership of Cultural Property, to which both France and the U.S. are signatories.

David Killion, the U.S. Ambassador to the U.N. cultural agency, who had voiced strong support for the Native American tribes in the past days, issued a statement Wednesday ― co-written by the U.S. Embassy ― calling the charity’s move a “generous act.”

But Killion suggested that the battle for Native American property rights was by no means over.

“The need for real dialogue in advance of such public sales, along with stronger legal protections, was once again made apparent this week,” added the statement, reiterating U.S. officials’ position that countries such as France tighten laws to protect important sacred objects.

Though there will be no celebrations in the Hopi tribe, with many Katsinam masks still in commercial circulation, the news was met with optimism.