25 U.S.C. § 1623: Special rules relating to Indians

(a) No Cost-sharing for Indians with income at or below 300 percent of poverty enrolled in coverage through a State ExchangeFor provisions prohibiting cost sharing for Indians enrolled in any qualified health plan in the individual market through an Exchange, see section 18071(d) of title 42. (b) Payer of last resortHealth programs operated by the Indian Health Service, Indian tribes, tribal organizations, and Urban Indian organizations (as those terms are defined in section 1603 of this title) shall be the payer of last resort for services provided by such Service, tribes, or organizations to individuals eligible for services through such programs, notwithstanding any Federal, State, or local law to the contrary.