The Anti-Assignment Act, 31 U.S.C.S.§ 203, does not apply to assignments by operation of law, as distinguished from voluntary assignments. Hence, transfer of a claim for accrued rent to a transferee of property under lease to the United States does not fall within the proscription of the federal anti assignment statutes. There are two types of voluntary assignments that are recognized as exceptions to the broad applicability of the Anti-Assignment Act: transfers by will and general assignments for the benefit of creditors. Likewise, a claim for patent infringement by the United States does not fall within the voluntary assignment proscription of the federal anti assignment statutes. A transfer of a claim against the United States that is made as a result of a consolidation or merger of a claimant corporation is involuntary, and thus not in violation of the federal anti assignment statutes.