There is a growing body of literature in this area.

Here are some volumes that might help you get started:

Feldman, Weil and Biederman.  Art Law.  I & II  Little, Brown, 1986

Malaro.  A Legal Primer on Managing Museum Collections.  Smithsonian,
1985

Merryman and Elsen.  Law, Ethics and the Visual Arts.  I & II  Penn,
1987

Phelan.  Museums and the Law.  AASLH, 1982