25 C.F.R. § 16.3
The statutory duties of the Secretary to furnish legal advice to any Indian of the Five Civilized Tribes, and to represent such Indian in State courts, in matters affecting a restricted interest owned by such Indian, shall be performed by attorneys on the staff of the Solicitor, under the supervision of the Field Solicitor. Such advice and representation shall be undertaken to the extent that the Field Solicitor in his discretion shall consider necessary to discharge said duties, with due regard to the complexity of the legal action contemplated, the availability of staff attorneys for such purposes, the value and extent of the restricted interests involved, possible conflicts between Indians claiming to be owners of such interests, the preference of such owners concerning legal representation, the financial resources available to such owners, the extent to which such owners require similar legal services in connection with their unrestricted properties, and any other factor appropriate for consideration.
25 C.F.R. § 16.3