According to 31 USCS § 3727, an assignment of any part of a claim against the United States Government may be made only after a claim is allowed, the amount of the claim is decided, and a warrant for payment of the claim has been issued.  Moreover, the assignment shall specify the warrant, must be made freely, and must be attested by 2 witnesses.  The person making the assignment shall bring it before an official who may acknowledge a deed and the official shall certify the assignment. The certificate shall state that the official completely explained the assignment when it was brought before him.

According to 41 USCS § 15, no contract shall be transferred by the party to whom the contract is given to any other party, if the United states government is involved, and that such an assignment annuls the contract transferred.

The above stated federal anti assignment statute provides an exception for some assignments to financial institutions.  In addition to the above two general anti assignment statutes, there are a number of federal statutes referring to the assignability of specific claims or types of claims.  An assignment of a claim for compensation is referenced in 5 USCS § 8130.  Likewise, there are federal statutes that refer to the assignability of national park contracts or leases, copyrights, trademarks, Indian contracts, oil or gas leases on public land, patents, federal pensions, social security benefits, and pay for members of the armed forces.

The federal anti assignment statutes’ intent is to protect the government.  The main purpose of the statutes is ensuring that the United States deals with one claimant only, preventing trafficking in claims against the government, and retaining defenses and counterclaims that might not be available against the assignee.

The general federal assignment statute (31 USC 203) invalidates all assignments of claims against the U.S.  Therefore, a voluntary assignment by the vendor of land to the purchaser of a claim against the United States for damages caused to buildings thereon cannot be enforced against the U.S.  Since federal anti assignment statutes exist to protect the government, assignment of claims against the U.S. is enforced between the parties according to the equities, without regard to whether the U.S. has paid or allowed the claim.