We turn now to that texas man we were telling you about arrested on a highway holding a sign warning about a speed trap just down the road. Now, he argues, he was just exercising his first amendment... See More
We turn now to that texas man we were telling you about arrested on a highway holding a sign warning about a speed trap just down the road. Now, he argues, he was just exercising his first amendment rights. Police don't see it that way. Abc's linsey davis has more. Reporter: Ron martin says he recorded his own arrest. Let go of the sign. Reporter: To show his side of the story in a flap with cops over a speed trap. Am I being arrested. I told you it's a violation of city ordinance -- Reporter: While they were conducting speed enforcement in october, martin was in the Drop it on the ground. Reporter: Holding up a sign with a hand painted warning to lead footed drivers, police ahead. You can't post a sign on public property. The problem that he has is not what his sign says, but it's where he was standing at the time. Reporter: Martin and his sign, police say, are a regular sight in the neighborhood. Something martin considers as just doing his part in the war on speed. You kind of nip it in the bud. Slow people down which the sign has been very effective. Reporter: He says he and the police are on the same side. Ultimately we're trying to do the exact same thing. I'm not wearing a police uniform. Reporter: Police disagree due in court next month on a misdemeanor charge, essentially a traffic ticket but the arrest was a violation of his first amendment right, he says. Regardless of his intentions, police say martin has been warned about his approach to public safety and asked that the public understand, quote, procedures we are required to follow. Mr. Martin, let go of the sign. Reporter: For "good morning america," linsey davis, abc news, new york.
This transcript has been automatically generated and may not be 100% accurate.