The requirements for Cage Codes are laid out in FAR subpart 4.18, which says that contracting officers shall verify the offeror's CAGE code (in SAM when applicable). If FAR provision 52.204-16 was added to the solicitation, then the contractor would have had to "provide its CAGE code with its offer with its name and location address or otherwise include it prominently in its proposal. The CAGE code must be for that name and location address. Insert the word "CAGE" before the number. The CAGE code is required prior to award" IAW with that provision. Then FAR clause 52.204-18 requires the contractor to maintain their CAGE code and report any changes to the contracting officer within 30 days after the change. Check to see if FAR clause 52.204-18 is in your contract and if it is, then the contracting officer can enforce its terms.