Police cannot punish drivers for flashing their headlights to warn others of speed traps, a federal judge has ruled (pdf) in a case involving the First Amendment.

The ruling arose after police in Ellisville, Missouri, ticketed Michael Elli for using his headlights to inform motorists that officers were lying in wait to ticket those exceeding the speed limit.

The American Civil Liberties Union (ACLU), which sued on behalf of Elli and other drivers, argued that the plaintiffs’ actions constituted a form of free speech.

U.S. District Judge Henry Autrey agreed with the ACLU and granted a preliminary injunction that prevents Ellisville police from ticketing or arresting any more motorists for flashing their headlights.

Autrey wrote that the officer in Elli’s case “did not have reasonable suspicion to believe that Plaintiff had violated any law” and that it was not illegal to warn drivers “because a speed trap is ahead.”

Other towns have tried to do the same thing with motorists warning each other.

ACLU Legal Director Tony Rothert said the ruling, the first of its kind in the nation, should apply everywhere. If not, the civil liberties group may file more lawsuits.

“We’re going to hope that they take note of the court’s order. And if we hear about it happening after today, we will contact them, and ask them to stop,” Rothert told the St. Louis Post-Dispatch.

Eugene Volokh, who teaches free speech law at UCLA, says he’s not sure if Elli’s and others’ actions are covered under the First Amendment.

“Whether this is the right answer is not clear. The situation is a special case of warnings to hide one’s illegal conduct because the police are coming — ‘abort the plan to rob the store’ or ‘flush the drugs down the toilet,’” Volokh wrote in The Washington Post.

-Noel Brinkerhoff

To Learn More:

Is Flashing Headlights to Warn of a Speed Trap Protected by the First Amendment? (by Robert Patrick, St. Louis Post-Dispatch)

Flashing Headlights to Warn Drivers of a Speed Trap = Constitutionally Protected Speech (by Eugene Volokh, Washington Post)

Flashing Lights to Warn of Speed Traps Is Shielded (by David Lee, Courthouse News Service)

Michael Elli v. City of Ellisville (U.S. District Court, Eastern Missouri) (pdf)

Driver Ticketed for Warning Others about Speed Trap Sues City (by Noel Brinkerhoff, AllGov)