((a)) Except as provided in subsection (b), funds appropriated to the Department of Defense may not be obligated or expended for the purpose of entering into a contract for the performance of firefighting or security-guard functions at any military installation or facility.

((b)) The prohibition in subsection (a) does not apply to the following contracts:

((1)) A contract to be carried out at a location outside the United States (including its commonwealths, territories, and possessions) at which members of the armed forces would have to be used for the performance of a function described in subsection (a) at the expense of unit readiness.

((2)) A contract to be carried out on a Government-owned but privately operated installation.

((3)) A contract (or the renewal of a contract) for the performance of a function under contract on .

((4)) A contract that is—

((A)) for a period of one year or less; and

((B)) covers the performance of functions that, in the absence of the contract, would have to be performed by members of the armed forces who are not readily available to perform such functions.