; and (B) enter into agreements and cooperation only with entities that recognize for collective bargaining purposes, and commit to collectively bargain with, any labor organization that has a written majority authorization among employees who participate in activities related to the agreement or cooperation with the Civilian Climate Corps. (2) Written majority authorization In this subsection, the term written majority authorization means writings signed and dated by a majority of employees in any appropriate unit in the form of authorization cards, petitions, or other suitable written evidence to designate a labor organization as the representative of such employees for the purpose of collective bargaining. (n) Tribal sovereignty The Director shall ensure that Civilian Climate Corps activities carried out under the national climate service program that affect individuals in Indian country are carried out in a manner that ensures that— (1) the sovereignty of Indian tribes and their conservation efforts are maintained; and (2) the national climate service program operates in consultation with the affected individuals in Indian country. (o) Buy American To the maximum extent practicable, the Director shall ensure that— (1) the materials used to carry out projects under this section are substantially manufactured, mined, and produced in the United States in accordance with chapter 83 of title 41, United States Code (commonly known as the Buy American Act )