To warn fellow motorists about the presence of police, some drivers will flash their headlights to indicate that cops are around. While this seems like a pretty harmless action, some states have prosecuted people for doing so. But so far, when these cases have come before the court, the judges have knocked them down. In America, there is freedom of expression, which is a constitutional right. This right has some limitations (like yelling “fire” in a crowded theater), but generally people can say what they please. Flashing headlights is a form of expressive behavior; the person in this case flashing the headlights is sending a message to others that police are around. It is an expressive message so long as the other person would be capable of understanding it.
All drivers know that when they see a driver flashing their lights at them that either they should a) use caution or b) turn on their lights. A case came before the U.S. District Court in Missouri in front of Judge Henry E. Autrey. In that case, the town of Ellisville prosecuted drivers who flashed their lights to warn of radar and speed traps. Judge Autrey issued a permanent injunction. Similarly, a man in Oregon was given a $260 ticket for flashing his headlights to warn other drivers about police; that judge also ruled in favor of the driver. Other states have taken notice, one of them being New Jersey. New Jersey Assemblyman Ronald S. Dancer introduced a bill which will make it permissible to flash headlights to oncoming motorists.
In Georgia, it is not illegal to flash your lights to warn oncoming motorists of police presence or other danger. The only thing you have to worry about is dimming your lights when another motorist is approaching.