Mark May, a self-employed carpet cleaner from rural western Indiana, was driving his car through the town of Terre Haute on Aug. 17 when he spotted an Indiana State Police patrol car zooming up from behind.

As May slowed at an intersection, the police vehicle cut in front of him — too aggressively, May thought, according to his federal lawsuit. If May had pulled that maneuver in front of a police officer, he would have earned a ticket, he believed. May correctly guessed that the trooper was pulling ahead to stop another motorist, and as he passed the patrol car, he signaled his displeasure.

He waved a middle-finger in the trooper’s direction.

The universal single-digit gesture of contempt is now the center of a federal lawsuit May filed last week against the man behind the patrol car’s wheel, Indiana State Police Master Trooper Matt Ames. According to the legal complaint, after seeing May’s middle-finger, Ames went after the driver, issuing him a ticket for “provocation,” the Washington Post reports.

But May’s middle finger is his constitutional right, his attorneys from the American Civil Liberties Union argue.