25 USC 956 - Claims against allotments

(a) Assignment, sale, hypothecation, attachment or levy void unless approved 
Equalization allotments made pursuant to this subchapter shall not be subject to assignment, sale, or hypothecation or to any attachment or levy for claims or debts created before or after September 21, 1959, without the written approval of the Secretary, and any such assignment, sale, hypothecation, attachment, or levy that has not been so approved by the Secretary shall be absolutely null and void.
(b) Liens and lis pendens; legal services 
No equalization allotment made pursuant to this subchapter, and no basic allotment made prior to this Act, shall be subject to an equitable charging lien or other charge or lien or enforced sale for any advantage or benefit which the allottee has received or will receive under or as a consequence of enactment of this subchapter, nor shall any lis pendens heretofore or hereafter filed upon such lands while in a restricted status be of any effect or constitute notice of any action. Whoever directly or indirectly accepts or receives any money or other form of compensation for legal services in connection with such restricted lands from any person who has not expressly employed him as his attorney shall be liable, in a civil action brought by the payor or his heirs or devisees or by the United States on his behalf, for twice the amount so accepted or received unless, prior to the time of acceptance or receipt of said compensation, the right to such compensation has been determined and the amount thereof fixed by a formal order of the Federal court having jurisdiction to make such order. Nothing herein provided shall be construed to prevent any attorney from petitioning the Federal court having jurisdiction to fix and determine the fees to which he is entitled and to pursue and enforce payment thereof in any lawful manner after the court has made such order.