The American Civil Liberties Union is hoping that a federal judge’s ruling earlier this month that temporarily barred Ellisville, MO from punishing drivers for using their headlights to warn others of speed traps will itself serve as a warning to other cities who try to do the same.

ACLU Legal Director Tony Rothert told the St. Louis Post-Dispatch that it was the first federal court ruling on the issue anywhere in the country. “It is legal in Missouri to communicate in this manner,” he said, “and detaining, ticketing or arresting someone for the content of their speech is illegal.”

In an online survey last week we asked you, our GasBuddy audience, to let us know how often you engage in this practice and more than 18,000 responded. Two-thirds of respondents said they have flashed to warn others.

19 percent said they 'Usually' flash; 25% said 'sometimes'; 20 percent said 'Occasionally' and 34 percent said 'Never.'

U.S. District Judge Henry Autrey’s preliminary injunction says that Michael J. Elli would likely prevail in a free speech lawsuit against Ellisville. Autrey’s ruling says that the officer “did not have reasonable suspicion to believe that Plaintiff had violated any law” and that it is not illegal to warn drivers “because a speed trap is ahead.”

The ACLU sued on behalf of Elli and other drivers last year, saying that drivers using their headlights to communicate about a speed trap — or another reason to proceed with caution — are protected by the First Amendment.

Rothert said that after Elli’s suit, they heard from drivers that other jurisdictions in Missouri and Illinois were also ticketing drivers for warning of speed traps, although the Post-Dispatch could not confirm current ordinances or enforcement actions with any of the named jurisdictions.

The ruling in Missouri is good news for all motorists. While some cash-strapped towns will undoubtedly continue to set up speed traps and red-light cameras to rob us of as much as they can get away with they should not be able to penalize you for 'obstruction' when you flash other motorists to communicate your warning of a speed trap. That's a victory for free speech.