A federal appeals court is reinstating a civil rights lawsuit brought by a New York man arrested for disorderly conduct after flipping off a police officer in traffic.

There's no law against directing to police what might be the world's oldest insulting gesture. Flipping the bird, or sticking out the middle finger, dates to ancient Greece and was adopted by the Romans as digitus impudicus – the impudent finger.

But it's not advised, as it may lead to a confrontation. And that's exactly what happened in upstate New York.

After the police stop in 2006, words were exchanged between the local police officer and middle-finger-saluter John Swartz, a 62-year-old Vietnam veteran. He flipped the bird at officer Richard Insogna who was employing a radar device to ticket speeders – and Insogna stopped the vehicle.

In reinstating the lawsuit, the 2nd U.S. Circuit Court of Appeals didn't buy Insogna's explanation for the traffic stop. Insogna testified in a deposition that he stopped the vehicle Swartz was traveling in because the raised middle finger suggested Swartz "was trying to get my attention for some reason" and that he "was concerned for the female driver."

A federal judge sided with police and tossed the lawsuit. But the New York-based appeals court on Thursday reinstated the case, which was also brought by the driver, Swartz's wife, Judy Mayton-Swartz.

According to the three-judge panel: (.pdf)

Perhaps there is a police officer somewhere who would interpret an automobile passenger's giving him the finger as a signal of distress, creating a suspicion that something occurring in the automobile warranted investigation. And perhaps that interpretation is what prompted Insogna to act, as he claims. But the nearly universal recognition that this gesture is an insult deprives such an interpretation of reasonableness. This ancient gesture of insult is not the basis for a reasonable suspicion of a traffic violation or impending criminal activity. Surely no passenger planning some wrongful conduct toward another occupant of an automobile would call attention to himself by giving the finger to a police officer.

No trial date has been set in the unlawful-arrest case. The disorderly conduct charges were later dropped after Swartz's arrest.

In its Thursday opinion, the appeals court cited American University legal scholar Ira Robbins, who has written a definitive paper on flipping the bird: "Digitus Impudicus: The Middle Finger and the Law." (.pdf)

In the paper, he writes: "The pursuit of criminal sanctions for use of the middle finger infringes on First Amendment rights, violates fundamental principles of criminal justice, wastes valuable judicial resources, and defies good sense."

This isn't the first lawsuit on the topic, and it likely won't be the last.

In 2009, a Pittsburgh man was awarded $50,000 after he was wrongly cited for disorderly conduct after flipping off an officer. A year later, suburban Oregon police department paid a local man $4,000 to settle a civil rights lawsuit in which he claimed he was pulled over for flipping off the cops in traffic.