“It’s difficult,” he said, “when there’s someone else deciding what’s art and what’s cultural patrimony.”

Legally, there’s little Riley––or any Native American tribe––can do to stop the auction. In the U.S., the Native American Graves Protection and Repatriation Act gives tribes a right to claim an artifact of cultural or religious significance from museums. But internationally, the U.S. has little legal say over transactions involving Native American artifacts, as was seen the previous times French auction houses put them up for sale.

On one occasion, in 2013, Néret-Minet Tessier & Sarrou, an auction house, planned to sell 70 artifacts, most of them headdresses the Hopi regard as sacred. The Hopi live in northeastern Arizona, and their tribal council tried to stop the auction. Their chairman, LeRoy Shingoitewa, even likened it to walking into a church, yanking down the cross, then sticking it in the ground to use as a fence post. The fight over the auction gathered international attention, and when a reporter with the news site Indian Country asked the company’s auctioneer, Gilles Néret-Minet, if the negative publicity would stop the auction, Néret-Minet replied: “No—because France is a country of rights!”

The Hopi sent the auction house a copy of their constitution that outlaws selling religious items and filed several lawsuits. But the French courts sided with the sellers.

France has long been a center for the sale of tribal artifacts from much of the world, and many of these objects are prized by collectors. But for the people to whom these objects originally belonged, the items possess religious or historical value—and they want them back. That’s the root of a fear not only in France, but across other Western countries, as well. It’s a fear perhaps best articulated by Néret-Minet, when he spoke about demands to return the Hopi headdresses.

“If they can claim these objects now,” he told Indian Country in 2013, “then African art is over, and the Cluny museum [of medieval objects, in Paris] would give back all of its pieces to the churches. If we are questioning the principle of ‘religious art,’ we should question the entire notion of art.”

The auction went forward in April 2013, making $1.2 million. One of the winners was Monroe Warshaw, an American art collector and exhibitor who bought two of the “Katsina” ceremonial headdresses, some of the most sacred objects of the Hopi people. Warshaw had little idea of the items’ history, or of the controversy around them. Of his impulsive buy, he simply thought they were gorgeous, he told me. “I had never seen such things.”

Warshaw saw beauty, history, and inspiration in the headdress. They were the qualities a collectors wants in art. But the Hopi saw more—as did the Acoma Pueblo tribe in a battle shield that is up for sale next week in Paris. The Acoma have lived on their land, about an hour from Albuquerque, New Mexico, for more than 800 years. When Riley, the Acoma governor, learned the shield was being auctioned, he consulted the tribe’s religious leaders who asked their office of historic preservation to investigate.