In this subchapter: (1) BIA The term “ BIA ” means the Bureau of Indian Affairs . (2) Department The term “ Department ” means the Department of the Interior . (3) Secretary The term “ Secretary ” means the Secretary of the Interior. (4) Under Secretary The term “ Under Secretary ” means the Under Secretary for Indian Affairs established under section 5633(a) of this title . ( Pub. L. 114–178, title III, § 302 , June 22, 2016 , 130 Stat. 439 .)