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.