It is the duty of the sheriffs, undersheriffs, and deputies to keep and preserve the peace in their respective counties, and to quiet and suppress all affrays, riots, and unlawful assemblies and insurrections. For that purpose, and for the service of process in civil or criminal cases, and in apprehending or securing any person for felony or breach of the peace, they, and every coroner, may call to their aid such person of their county as they may deem necessary.
C.R.S. § 30-10-516
For authority of a peace officer to command aid, see § 16-3-202.