The Native American Graves Protection and Repatriation Act (NAGPRA) was passed in 1990. In part, it provides legal protections for Native American human remains equal to those of other American citizens, and is one of the most significant cultural policy laws ever enacted in the United States. Despite intense lobbying against it by both museum and anthropological organizations, the law provides legal means for Native American human remains, burial goods, and certain other cultural objects to be returned to tribal communities from museums and government agencies.

A key condition for returns is that tribes must prove they are related to human remains and objects. This proof may include oral traditions as well as geographical, historical, archaeological, and other information, and is based on a "preponderance of the evidence," rather than scientific certainty.

Government agencies such as the U.S. Army Corps of Engineers, on whose land Kennewick Man was found, are required to report such discoveries to potentially affiliated tribes. The tribes can then decide, under NAGPRA law, to request return of the remains and of any associated objects. Kennewick Man is subject to NAGPRA if he is defined as being Native American. His bones can then be repatriated if one or more tribes prove their cultural affiliation to him.

• The law requires that any affected Native American tribe be promptly notified when any human remains or cultural objects are accidentally found on any federal or tribal lands.
• The law requires that affected Native American tribes approve any permits for the intentional excavation of human remains or cultural objects on any federal or tribal lands.
• The law imposes criminal penalties for any trafficking of Native American human remains or specified cultural objects.
• The law requires that American museums and other public collections with Native American human remains or cultural objects provide tribes with detailed collection information and access, and repatriate to tribes, on request, human remains and cultural objects that meet the law's criteria.