Justice Manual § 5-14.420

The Department of Justice generally does not oppose permissive intervention by Indian tribes in litigation where the Department of Justice has brought suit to protect the real property interests of tribes held in trust or restricted fee, or the intervention of members of Indian tribes where the Department has brought suit to protect the real property interests in trust or restricted fee of individual Indians. Similarly, when the Department of Justice is defending agency action, regulations, or statutes, it generally does not oppose permissive intervention as a defendant by the tribe(s) or individual Indian(s) benefiting from these statutes, regulations or agency actions. The Department, however, usually takes the position that such tribes or their members are not necessary parties pursuant to Federal Rule of Civil Procedure 19. The United States generally is capable of adequately protecting the interest of a tribe, as well as other nonparties that share an interest in seeing the action upheld. Thus, in practice, neither affirmative suits nor cases challenging agency action usually require joinder of other interested parties. Where the interested nonparty is a tribe or a member of a tribe, and the underlying agency action being challenged is premised on the federal government's trust responsibility to the tribe or member of the tribe, the likelihood that the United States will adequately represent that interests is even stronger. See Washington v. Daley, 173 F.3d 1158, 1168 (9th Cir. 1999).