25 C.F.R. § 225.33
An assignment of a minerals agreement, or any interest therein, shall not be valid without the approval of the Secretary and, if required in the minerals agreement, the Indian mineral owner. The assignee must be qualified to hold the minerals agreement and shall furnish a satisfactory bond conditioned on the faithful performance of the covenants and conditions thereof as stipulated in the minerals agreement. A fully executed copy of the assignment shall be filed with the Secretary within five (5) working days after execution by all parties. The Secretary may permit the release of any bonds executed by the assignor upon submission of satisfactory bonds to the Bureau of Indian Affairs by the assignee, and a determination that the assignor has satisfied all accrued obligations.
25 C.F.R. § 225.33