The Federal Acquisition Regulation (FAR) is the principal set of rules regarding federal government procurement in the United States, and is codified at Chapter 1 of Title 48 of the Code of Federal Regulations, 48 CFR 1. It covers many of the contracts issued by the US military and NASA, as well as US civilian federal agencies.

The largest single part of the FAR is Part 52, which contains standard solicitation provisions and contract clauses. Solicitation provisions are certification requirements, notices, and instructions directed at firms that might be interested in competing for a specific contract. These provisions and clauses are of six types: (i) required solicitation provisions; (ii) required-when-applicable solicitation provisions; (iii) optional solicitation provisions; (iv) required contract clauses; (v) required-when-applicable contract clauses; and (vi) optional contract clauses."

If the FAR requires that a clause be included in a government contract, but that clause is omitted, case law may provide that the missing clause is deemed to be included. This is known as the Christian Doctrine, which is based on the underlying principle that certain government regulations have the force and effect of law, and government personnel may not deviate from the law without proper authorization. Prospective contractors are presumed to know the law, including the limits of the authority of government personnel. Thus, a mandatory clause that expresses a significant or deeply ingrained strand of public procurement policy will be incorporated into a Government contract by operation of law, even if the parties intentionally omitted it.

A contract award can be challenged and set aside if a protester can prove that either the contracting agency or the contract awardee did not comply with the requirements of the solicitation. A successful protest can result in reconsideration of the decision to award the contract or award of the contract to the protester in lieu of the original awardee. Even though a successful protester may not ultimately be awarded the contract, the government agency may have to pay the protester's bid and proposal costs.