N.M. Stat. § 29-1-9
No sheriff of a county, mayor of a city or other person authorized by law to appoint special deputy sheriffs, marshals, policemen or other peace officers in the state of New Mexico to preserve the public peace and to prevent and quell public disturbances shall appoint as such special deputy sheriff, marshal, policeman or other peace officer any person who shall not be a citizen of the United States of America. No person shall assume or exercise the functions, powers, duties and privileges incident and belonging to the office of special deputy sheriff, marshal, policeman or other peace officer without first having received an appointment in writing from a person authorized by law to appoint special deputy sheriffs, marshals, policemen or other peace officers; provided that nothing in this section shall apply to lawfully appointed United States marshals or to deputies of those marshals or to railroad peace officers appointed pursuant to Section 63-2-18 NMSA 1978 in the performance of their duties as peace officers.
This section shall not apply in times of riot or unusual disturbance and when so declared by the public proclamation of the governor of the state.
NMS § 29-1-9