34 U.S.C. § 20929

(a) Election (1) In general A federally recognized Indian tribe may, by resolution or other enactment of the tribal council or comparable governmental body— (A) elect to carry out this part as a jurisdiction subject to its provisions; or (B) elect to delegate its functions under this part to another jurisdiction or jurisdictions within which the territory of the tribe is located and to provide access to its territory and such other cooperation and assistance as may be needed to enable such other jurisdiction or jurisdictions to carry out and enforce the requirements of this part. (2) Imputed election in certain cases A tribe shall be treated as if it had made the election described in paragraph (1)(B) if— (A) it is a tribe subject to the law enforcement jurisdiction of a State under section 1162 of title 18 ; (B) the tribe does not make an election under paragraph (1) within 1 year of July 27, 2006 or rescinds an election under paragraph (1)(A); or (C) the Attorney General determines that the tribe has not substantially implemented the requirements of this part and is not likely to become capable of doing so within a reasonable amount of time. (b) Cooperation between tribal authorities and other jurisdictions (1) Nonduplication A tribe subject to this part is not required to duplicate functions under this part which are fully carried out by another jurisdiction or jurisdictions within which the territory of the tribe is located. (2) Cooperative agreements A tribe may, through cooperative agreements with such a jurisdiction or jurisdictions— (A) arrange for the tribe to carry out any function of such a jurisdiction under this part with respect to sex offenders subject to the tribe’s jurisdiction; and (B) arrange for such a jurisdiction to carry out any function of the tribe under this part with respect to sex offenders subject to the tribe’s jurisdiction.