28 CFR 0.197: Agreements, in connection with criminal proceedings or investigations, promising non-deportation or other immigration benefits.

The Immigration and Naturalization Service (Service) shall not be bound, in the exercise of its authority under the immigration laws, through plea agreements, cooperation agreements, or other agreements with or for the benefit of alien defendants, witnesses, or informants, or other aliens cooperating with the United States Government, except by the authorization of the Commissioner of the Service or the Commissioner's delegate. Both the agreement itself and the necessary authorization must be in writing to be effective, and the authorization shall be attached to the agreement.