The St Louis Art Museum claimed in 2010 , when asked about the return of requests for the return of the Lady Ka-Nefer-Nefer mummy mask, that “we would do the right thing … if there was something that refuted the legitimacy of the provenance“.
The courts have now ruled that they can keep the mask – although a lot of questions have to be asked, about how something that was know to have previously been on display on another museum & then went missing, can be considered an entirely legitimate purchase without first discussing the matter with the original owners.
David Gill has a lot more commentary on the case on his Looting Matters website .
Washington Post 
Federal judge rules 3,200-year-old Egyptian mummy mask can remain at St. Louis Art Museum
By Associated Press, Published: April 5
ST. LOUIS — A St. Louis museum can keep hold of a 3,200-year-old mummy’s mask, a federal judge has ruled, saying the U.S. government failed to prove that the Egyptian relic was ever stolen.
Prosecutors said the funeral mask of Lady Ka-Nefer-Nefer went missing from the Egyptian Museum in Cairo about 40 years ago and that it should be returned to its country of origin. The St. Louis Art Museum said it researched the provenance of the mask and legitimately purchased it in 1998 from a New York art dealer.
U.S. District Judge Henry Autry in St. Louis sided with the museum.
The U.S. government “does not provide a factual statement of theft, smuggling or clandestine importation,” Autry wrote in the March 31 ruling.
“The Government cannot simply rest on its laurels and believe that it can initiate a civil forfeiture proceeding on the basis of one bold assertion that because something went missing from one party in 1973 and turned up with another party in 1998, it was therefore stolen and/or imported or exported illegally,” the judge wrote.
A message left with Egypt’s Supreme Council of Antiquities was not returned.
The 20-inch-long funeral mask of painted and gilded plaster-coated linen over wood with inlaid glass eyes was excavated from one of the Saqqara pyramids, about 16 miles south of Cairo, in 1952. Ka-Nefer-Nefer was a noblewoman who lived from 1295 BC to 1186 BC.
U.S. government investigators suspect the mask was stolen sometime between 1966, when it was shipped to Cairo for an exhibit, and 1973, when the Egyptian Museum discovered it was missing.
The art museum bought the mask in 1998 for $499,000 from a New York art dealer, and it has been on display at the museum in Forest Park ever since.
U.S. Attorney Richard Callahan said a decision on whether to appeal has not been made.
“We’re just looking to make sure we haven’t missed the tiniest bit of circumstantial evidence,” Callahan said. “We’re back to the drawing board and studying it.”
Museum officials have said they researched the mask’s ownership history before buying it and had no indication there were questions about how it arrived in the U.S. The museum’s research showed the mask was part of the Kaloterna private collection during the 1960s, before a Croatian collector, Zuzi Jelinek, bought it in Switzerland and later sold it to Phoenix Ancient Art of New York in 1995. The art museum purchased the mask from Phoenix Ancient Art.
St. Louis Art Museum attorney David Linenbroker said the museum is confident the ruling will mean that the mask can remain permanently in St. Louis.
“We don’t have any interest in possessing a stolen object,” Linenbroker said. “We’ve been facing all this innuendo for years.”
He said the legal process provided an opportunity for someone to prove the mask had been stolen, but no one did.
“We’re confident we’re the rightful owner,” Linenbroker said.