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An Oregon man's public criticism of the mathematical formula used by red light cameras got him in trouble — not with the police but with the state engineering board.

So he's suing, claiming a violation of free speech.

After his wife got a ticket based on a red light camera in Beaverton, Oregon, Mats Järlström, a Swedish-born electronics engineer, studied the calculations used to determine the length of the yellow light cycle. He concluded it was too short, because it failed to account for the longer time a driver needed to turn a corner, rather than go straight through the intersection.

Convinced the cameras were using an out-of-date formula, he took his message to practically anyone who would listen — local TV stations, a conference of traffic engineers, and even the state board of engineer examiners.

Mats Järlström in Beaverton, Oregon was fined $500 by speaking about engineering issues without a license, according to the board of engineer examiners, when he studied the calculations used to determine the length of the yellow light cycle after his wife received a ticket based on a red light camera. Institute for Justice

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That's what got him in trouble.

The board fined him $500 and said he was violating a state law by speaking about engineering issues without a license.

"By providing the public with his traffic engineering calculations," the board said, "Järlström engaged in the practice of engineering." And since he didn't have a license issued by the state, he was violating the law, it said.

Now he’s suing in federal court, accusing the state of violating his First Amendment right to speak about a public issue.

"Criticizing the government's engineering isn't a crime. It's a constitutional right," said Samuel Gedge of the Institute for Justice, a conservative public interest law firm representing Järlström. "You don't need to be a licensed engineer to talk about traffic lights."

Mats Järlström in Beaverton, Oregon was fined $500 by speaking about engineering issues without a license, according to the board of engineer examiners, when he studied the calculations used to determine the length of the yellow light cycle after his wife received a ticket based on a red light camera. Institute for Justice

As many states do, Oregon prohibits a person from practicing engineering without a license. But the state's board of engineering examiners equates publicly talking about engineering issues with practicing engineering.

"I was fined simply for speaking out and was told that I can't truthfully call myself an engineer. People should be free to debate any topic, including technical topics like math and traffic lights," Järlström said.

A spokesman for the state engineering board had no comment on the lawsuit, and the state has not yet responded in court.

Järlström paid the $500 fine. But he isn't suing to get his money back.

Another Institute for Justice lawyer on his legal team, Wesley Hottot, said the state is essentially requiring a permission slip to debate government policy. "This board and licensing boards across the country think the First Amendment doesn't apply to them. They couldn't be more wrong."