Well, your post #41 actually changed my mind. At first I agreed with the SC ruling, but now I don’t. The cop had no legal reason to stop that car. And, yes, a traffic cop should know all the traffic laws, each one of them. That’s his job. If he doesn’t know, it’s on him, and on him alone.
Reading the case further (it’s actually quite short, I recommend you do), seems the law in question was actually unclear, and could reasonably be read to mean two different conditions. As worded, a reasonable person could conclude just one broken lamp was enough to constitute a violation, while another reasonable person could conclude that the presence of multiple lights providing the same indication (most cars have at least 3 brake lights) means so long as one indicator works the vehicle & driver are legally OK.
When it takes a court ruling to discern what a particular law actually means, it is not unreasonable for the arresting officer to apprehend the suspect and let a judge make the final detailed determination.
The core issue of the case is that the officer is empowered to stop someone acting suspiciously and investigate further ... and may ask “may I search” to go where he is otherwise not empowered to. A cop may ask you for no reason “may I search your premises”; if you consent, you are liable for the results. If the driver had said “no” the contraband would not have been found; he attracted the cop’s attention, was further investigated, a warning issued based on a reasonable unclarity of law, a search request made based on reasonably suspicious behavior, the request approved, and the contraband found.
Sorry, but I’ve got to conclude there was no 4th Amendment violation. The warning could have been challenged in court (the only way the unclear law would get clarified) and thrown out, but that’s irrelevant to the fact that suspicion arose and the driver consented to search - he could have held his 4th Amendment right precisely by saying one word: “no.”
“The cop had no legal reason to stop that car.”
More concisely: the law was unclear and the cop proceeded with a reasonable, albeit ultimately overturned, interpretation of that law. It took a court case to clarify it, which could only come by a cop acting on the dissenting interpretation.