VA and IHS face unique challenges associated with consulting with a large number of diverse, sovereign tribes to implement the MOU, and lack fully effective processes to overcome these complexities. VA and IHS officials told us the large number (566 federally recognized tribes) and differing customs and policy-making structures present logistical challenges in widespread implementation of the MOU within tribal communities. They also told us that tribal sovereignty–tribes’ inherent right to govern and protect the health, safety, and welfare of tribal members–adds further complexity because tribes may choose whether or not to participate in MOU-related activities. Consistent with internal controls, VA and IHS have processes in place to consult with tribes on MOU-related activities through written correspondence and in-person meetings.