Officer will use HEIEN, PETITIONER v. NORTH CAROLINA. https://supreme.justia.com/cases/federal/us/574/13-604/opinion3.html
From the opinion "what if the police officer’s reasonable mistake is not one of fact but of law? In this case, an officer stopped a vehicle because one of its two brake lights was out, but a court later determined that a single working brake light was all the law required. The question presented is whether such a mistake of law can nonetheless give rise to the reasonable suspicion necessary to uphold the seizure under the Fourth Amendment. We hold that it can. Because the officer’s mistake about the brake-light law was reasonable, the stop in this case was lawful under the Fourth Amendment."
I thought ignorance of the law is not an excuse.