“Can they be jammed or thwarted?”
When you park your car just be sure to put on the car cover so it hides your plate. Nothing illegal about that at all.
No idea what to do about it when you’re driving.
Some companies sell reflective license plate covers
to thwarth these scanners
Problem is illegal in NJ
Will get ticketed for having one on your plate.......
I just carry around a bucket of mud - works just as well.