There are several different schools of thought concerning the powers of an off-duty police officer, and each police department has its own best practices policy. A duly licensed law enforcement officer generally has the authority to enforce the law 24 hours a day, seven days a week, but only after establishing his or her identity as a police officer. The designation "off-duty" only means the officer is not working a regular shift for the police department, not living as a private citizen with no authority whatsoever. An off-duty police officer can be employed as a private security guard and still have the power to arrest offenders or in many circumstances carry a concealed weapon.
This does not mean, however, that an off-duty police officer can use his or her authority for personal reasons. When not in uniform, a police officer has the same limited rights as any other citizen when it comes to personal responsibility and behavior. For example, an off-duty police officer attending a private party cannot pull a gun on a fellow guest or force an intoxicated party-goer to stop drinking. He or she can place a person under citizen's arrest until an on-duty police officer arrives, but many police departments discourage off-duty police officers from actively participating in such an arrest unless the situation is life-threatening.
An off-duty police officer may have proper identification and legal authority to arrest an offender, but he or she is also not considered to be on the clock, meaning there could be serious liability or insurance issues if he or she is injured during an off-duty incident or other damage occurs. This is why many off-duty police officers tend to avoid getting directly involved in minor incidents unless the offense is clearly egregious. An off-duty police officer may contact an on-duty police officer to report a minor traffic accident, but only use his or her authority to pull over an erratic driver creating a clear traffic hazard.
Some people believe that an off-duty police officer not in uniform and driving an unmarked car cannot legally issue a citation, but that is not always the case. Different police departments have different policies concerning the authority of off-duty officers, but in many places an off-duty police officer does have the legal right to detain an offender until an on-duty officer arrives to finish the process. The key factor in such an action is proper identification, however. An off-duty police officer who instigates a fight or commits an illegal act has no more rights or legal protections than any other private citizen.