Auxiliary police are usually the part-time reserves of a regular police force. They may be armed or unarmed. They may be unpaid volunteers or paid members of the police service with which they are affiliated. In most jurisdictions, Auxiliary Police officers are empowered to make arrests for crimes that occur in their presence.

In Canada, many police forces utilize the services of auxiliary constables. Under various provincial policing legislations and the Royal Canadian Mounted Police Act, the role of auxiliary constable is to assist regular, or sworn, police constables in the execution of their duties, as well as to provide assistance in community policing.

Auxiliary constables in Canada wear uniforms similar to regular force constables. However, most wear the word "auxiliary" on a rocker panel under the force's crest on each arm, and in some cases, wear a red and black checkered head band on their service caps to distinguish them from full-time police. Also, auxiliary constables are usually unarmed, but are trained in firearms. They may, depending on legislation and policies, carry a baton and handcuffs while on duty.