In response to a congressional request, GAO reviewed issues concerning the regulation of surface coal mining on Indian lands, focusing on: (1) the Indian assumption of regulatory authority over surface coal-mining operations; and (2) the Department of the Interior's proposal to reallocate the abandoned mine land (AML) reclamation funds currently set aside for Indian tribes. GAO determined that several issues could affect future legislative efforts to grant primacy to Indian tribes, including: (1) disputes over the definition of Indian lands outside the boundaries of the reservations and the states' historical regulatory role on these lands; (2) multiple regulatory authorities for mines that span federal, Indian, and state lands; (3) the adequacy of tribal judicial systems to enforce the Surface Mining Control and Reclamation Act's requirements; and (4) the ability of the tribes to impartially regulate coal mining operations in which they have vested interests. GAO found that, under the act, Interior has the legal authority to reallocate any AML funds not used by a state or Indian tribe within 3 years of the initial allocation.