That's what Ron Martin was charged with when local law enforcement in Frisco, Texas, arrested him for alerting oncoming motorists of the discreet enforcement via a “police ahead” sign.
A law aims to curb those from holding business signs on public property, although Martin says that doesn't apply to him as he's not operating as a business or aiming to profit from the venture.
Curiously, the man also says that he's not opposed to the idea of speed traps, and says that his behavior had the same (theoretical) motivations—to get drivers to slow down.
Most municipalities already warn in a general sense, via signs, usually at city limits, of traffic-law and speed enforcement; and some states have decided that it's legal for motorists to give alerts to others—in primitive form via headlights, for instance, or through more sophisticated electronic information via apps like Trapster.
The man's case is headed to a municipal court. Based on local reports, it's unclear if the motivations of this man and the arresting officers are as straightforward as said. How and to what degree can we inform others about 'hidden' speed enforcement?