You cannot be cited for another states motor vehicle traffic or sometimes referred to vechicle maintenance statutes/law while traveling etc, when you are not a resident of the state of the jurisdiction the police officer is representing.
So example, if you live in NJ and don't have a front plate, which is the law in NJ - 2 plates, and drive into PA, a PA cop cannot stop you and write a NJ statute, nor can they cite you for a PA law if PA was a dual plate state.
Funny to say this but you are safer in another state without your plate than your home state if its a 2 plate state.
I have no front plate on my challenger, no one cares, and neither do I. the plate holder is ugly, its not going on and thats that. on my TRX i run two plates but thats cause the plate holder was there already.
Source, ex-le.