25 C.F.R. § 162.357
May a lessee mortgage a residential lease?
(a) A lessee may mortgage a residential lease by meeting the consent requirements in § 162.358 and obtaining BIA approval of the leasehold mortgage under in §§ 162.359 and 162.360.
(b) Refer to § 162.349(b) for information on what happens if a sale or foreclosure under an approved mortgage of the leasehold interest occurs.