according to the New York Times. In some cases, museums argue that the statute of limitations has passed. In other cases, museums try to beat claimants to the courthouse and try to get themselves declared as the rightful owner.
"At stake," notes the New York Times, "in this emotional debate are the fate of valuable works of art, the reputations of elite cultural institutions and the legal issue of whether the American judicial system is capable of addressing restitution claims."
The Times story also includes a short video that offers some good background.