After the Second World War, the Allies returned many displaced artworks to the nations they'd been stolen from, the assumption being that the countries themselves would locate the rightful owners. Frequently, this didn't happen. And because many of the nations that received returned work were part of the Soviet Union, their archives were sealed until recently, making it impossible for survivors and their descendents to gain the evidence needed to press claims. Thus the dissolution of the USSR has provoked a rash of new claims.

Many U.S. museums maintain public registries of artwork whose provenance has gaps during the Nazi era (1933-1945). In September, a searchable national registry of such work, the Nazi-Era Provenance Internet Portal, will go live on the American Association of Museums' Web site. Several states are also in the process of enacting Holocaust exception legislation. The toughest of these is a California law that became effective in January 2003: It doesn't permit museums and other institutions to use the statute of limitations defense for any action commenced before the end of 2010.