Can public domain art be protected?

Dear Rich: I have a question. I know that old paintings like the Mona Lisa are not protected anymore, but I've heard that museums can still prevent reproductions of these paintings somehow. Is that true? How can that be? Yes, as a general rule, paintings that existed before 1923 are in the public domain and can be copied freely. However, museums have argued for years that their photographs of those paintings were protected under copyright, thus enabling them to control everything from postcard sales to artbook licensing. That ended in 1999 when a court ruled that "slavish reproductions" of visual works in the public domain are not copyrightable. (The photos may have required skill; but there was no originality.) In other words, you're free to reproduce replicas of public domain artwork in the U.S. Of course, many museums still limit photographic access to paintings and on that basis, people who want high quality reproductions still have to seek permission -- one reason why few people have seen this rare painting of Mona Lisa's sister, Drea, (or so many of Mona's other relatives).