Copyright and Contract in conflict?

Professor Eric Goldman’s Technology & Marketing Law Blog has an interesting article about the simmering dispute over copyrights in photographs of public-domain works of art.

It seems a public interest group recently downloaded scores of photographs from the Smithsonian Institution and posted them on the photo-sharing site flickr. The problem is… the Smithsonian’s ‘copyright’ page prohibits this type of exploitation of the images… even if they’re in the public domain.

Can contract law reach where copyright law doesn’t?