48 C.F.R. § 401.403
In individual cases, deviations from either the FAR or the AGAR will be authorized only when essential to effect a necessary acquisition or where special circumstances make such deviations clearly in the best interest of the Government. Except for cost principles, the Head of the Contracting Activity (HCA) may approve individual deviations from the AGAR, after coordinating with the Office of General Counsel (OGC) and the SPE. No deviations from the FAR or AGAR may be authorized by an individual contracting officer or an individual contracting office. A copy of each deviation and its supporting documents shall be provided to the SPE. Deviations from the FAR shall not be made unless such action is authorized by the SPE after consultation with the OGC and any other appropriate office, based on a written justification stating clearly the special circumstances involved.
48 C.F.R. §401.403