Supreme Court--police only have to think you violated a law

[JWC]

http://www.wsj.com/articles/supreme-court-gives-police-more-leeway-in-traffic-stop-case-1418665366

http://www.pbs.org/newshour/rundown/police-can-use-evidence-siezed-unrelated-traffic-stops-supreme-court-rules/

Quote:
The chief justice said police officers are accorded a margin of error when they make incorrect factual assessments in the field. The same should be true when they make mistakes of law, he said, because officers can confront situations where they have to make quick decisions on matters in which it isn't clear how a particular law applies.

A lot of people seemed to be upset with this ruling--calling it a step closer to the U.S. being a police state--and ripe for being abused. What I want to know is how much leeway is the public given in regards to making a mistake in understanding a law? In business law classes, we were always told ignorance of the law is no excuse--but here ignorance of the law seems to be an advantage.

I'm not sure this is really anything new, but now affirmed as the police being within their right to make questionable stops--and declare they didn't understand the law.

I've been pulled over for:
Demonstration of speed (revving my engine)
Headlamp out (it wasn't)
Driver's door not shut completely (wife was driving and got a ticket for not having her license with her.)
Driving through town after midnight. (No curfew, the officer was just curious why I was out at night.)

A friend was once pulled over and ticketed for obstructed view, the officer thought the windshield needed cleaning.

[GoCougs]

The core of the ruling is LE earning the privilege of leeway owing to the risk and importance of such a job and if such leeway didn't exist LE by and large wouldn't really work owing to the fear of reprisal.