Q: If a cop is driving their police car home, but they aren’t on duty, can they make a traffic stop? And can a cop from one city make a traffic stop in a different city?

A: Why does this sound like it’s not just a theoretical question? The short answer: yes and yes. The Washington Court of Appeals and the Revised Code of Washington provide the source material.

In 1982 a Lynnwood police officer asleep in his home at 2:30 a.m. woke up, looked out his window and saw someone prowling around his neighbor’s car. The officer went out, dressed only in a pair of pants, identified himself as a police officer, and attempted to arrest the prowler. The Court of Appeals was faced with the question of whether an off-duty officer has the same authority to make an arrest as an on-duty officer. In 1983 the court concluded, “We are convinced that he does.”

The judges referenced state law that says, “Any police officer having probable cause (followed by 16 examples of probable cause) shall have authority to arrest the person.” The ruling hinged, at least partly, on the word “any,” which they reasoned meant both on- and off-duty officers.

That court decision isn’t what made off-duty enforcement legal; the court was affirming that it already had been legal. That no one in Washington challenged that premise until 1983 suggests we already had a good understanding that an off-duty officer had enforcement authority. Maybe no one else bothered to challenge it because it had repeatedly been settled in other states. The earliest similar court conclusion I could find came from California in 1960.

But, you might argue, that law is about making arrests. We’re talking about traffic infractions. State law requires that people comply with any lawful order or direction of “any police officer.” If an off-duty officer can make an arrest wearing only his pants, it seems reasonable that an off-duty officer in a patrol car could give you a speeding ticket.

As to your question about traffic stops outside an officer’s jurisdiction, law states that a “general authority Washington peace officer” may enforce, with some limitations, the “traffic or criminal laws of this state throughout the territorial bounds of this state.”

I’m not sure what the law was prior to 1985, but it must have been problematic. That year the legislature passed the Washington mutual aid peace officers power act, stating that they wanted to modify the “current artificial barriers” to cooperative law enforcement. That act made it clear that an officer’s authority was statewide, and that officers could respond to emergencies and requests for law enforcement assistance outside the jurisdiction where they are employed.

I expect you’ll agree that we wouldn’t want an officer who is otherwise qualified and capable of intervening in an in-progress crime to be prevented from doing so by a political boundary. Given that traffic crashes take more lives than violent crime, it makes sense that the same authority would apply to traffic enforcement.

Doug Dahl writes a weekly column for this newspaper. He is with the state Traffic Safety Commission.