25 C.F.R. § 214.18
Approved leases or any interest therein may be transferred or assigned with the consent and approval of the Secretary of the Interior and not otherwise. Transfers or assignments, when so approved, shall be subject to the terms and conditions of the original leases and regulations under which such leases were approved as well as to such additional requirements as the Secretary of the Interior may prescribe. The transferee or assignee shall furnish with his transfer or assignment a satisfactory bond as prescribed in § 214.4 in connection with leases. Any attempt to transfer or assign an approved lease or any interest therein without the consent and approval of the Secretary of the Interior shall be absolutely void and shall subject the original lease to cancellation in the discretion of the secretary.
25 C.F.R. §214.18