"This is very unusual," Patty Gerstenblith, who directs the Center for Art, Museum & Cultural Heritage Law at DePaul University, told me not long after the museum filed its suit. "This is the first time I've seen a public institution like a museum deciding to expend its funds to proactively sue the government."

Now comes U.S. District Judge Henry E. Autrey, who on March 31 handed museum leaders a legal victory, and a moral challenge, when he dismissed the government's forfeiture claim, finding it "devoid of any facts showing that the Mask was 'missing' because it was stolen and then smuggled out of the country. " (Underline and bold in the original).

Indeed, there are no official records showing that the mask was sold by -- or stolen from -- the Egyptian government. Rather, Egyptian records indicate that the mask, excavated during a state-sponsored dig in the early 1950s, was registered to the Egyptian Antiquities Service. The government kept it in storage until 1966, when officials shipped it to Cairo for restoration. From there, the paper trail goes cold. It was not until seven years later, during a routine inventory in 1973, that the mask came up missing.

Legally, at least, the Ka-Nefer-Nefer simply vanished.

But the Egyptian record stands in stark contrast to the museum's own provenance for the mask, which has often been used to justify its possession of the 3,200-year-old artifact. According to that history, the mask entered the European art market around 1952, its presence confirmed by a lone Swiss businessman who mysteriously espied it during a trip to Brussels that year. (How the sellers knew, nearly half a century later, to contact the businessman about his serendipitous trip has never been adequately explained.)

The mask entered a private Swiss collection in the early 1960s, where it remained for roughly 30 years, until Phoenix Ancient Art, an elite antiquities firm with galleries in both Geneva and New York, acquired it, selling it to the St. Louis museum in 1998 for $499,000. Owned by the Lebanese brothers Ali and Hicham Aboutaam, Phoenix Ancient Art inhabits a rarefied world where a handful of dealers vie for the extremely rare, valuable or never before seen. Viewed in another light, this is a market whose emphasis on the hard-to-find means that plunder is often whitewashed, making it all but indistinguishable from the legitimate market.

The Federal Bureau of Investigations estimates that losses from art and cultural property crimes weigh in at as much as $6 billion annually. And while the illicit antiquities trade represents only a fraction of that number, experts contend that the antiquities market itself is awash with loot.

At times, this has meant trouble for the Aboutaams. The U.S. government returned a funerary slab to Yemen after the Aboutaams consigned it for auction at Sotheby's in 2003. The slab's provenance declared that it was held in a private collection, but investigators determined that it had actually been stolen from a Yemeni museum nearly a decade earlier. One year later, in 2004, a federal court in New York sentenced Hicham Aboutaam to one-year probation and a $5,000 fine after he pleaded guilty to a misdemeanor charge of misrepresenting the origin of an Iranian drinking vessel on customs documents. That same year, an Egyptian court sentenced his brother, Ali Aboutaam, to fifteen years in prison after finding him guilty in absentia of helping to smuggle antiquities out of the country. Ali Aboutaam remains free, however, and his co-defendants in the case were subsequently acquitted.