He never claimed to be a traffic or transportation engineer, in fact the fine cited him for use of the phrase "electronics engineer." He is an EE: He has an electrical engineering degree from his home country (Sweden) and he has worked as an electrical engineer for decades.
>I am a registered professional traffic engineer. As such, I feel that registration is very important and serves to protect the public at large from people producing work with little to no relevant experience.
"PE" (professional engineer) does have a legal distinction in the jurisdiction of Oregon, but he never claimed to be a registered PE in the state of Oregon. "Engineer" is not a legal distinction. He never made any false declarations about his credentials.
>the State Board did not censor what he was saying, they asked him to stop representing himself as an engineer.
They "asked him" by issuing a $500 fine in response to his letter for committing the apparent crime of sending a letter in which he (factually) stated that he is an engineer. Telling citizens "you are not allowed to write a letter to the government in which you use the word 'engineer' (a term with no legal distinctions) when describing yourself" sounds like censorship to me.