Also remember that under interstate traffic code agreements, what is legal in YOUR state of license is what is binding. For example, in Ohio, you have to have plates front and back on a car, whereas Indiana is rear only. You can't get pulled over or cited in Ohio for not having front plates.
In ***my*** training, this applied to other areas (but not all), including trailers (what size required what types of plates and what did not), Seat Belt laws, etc. For example, Indiana does not disallow radar detectors. For the sake of argument, if detectors HAD been illegal but I popped someone from a state where I know they are NOT, I would have let them go. Everyone is different, but we operated such that if we didn't know and/or weren't sure, we rarely ticketed.
This is a HUGE grey area and seldom discussed. 9/10ths of the officers out there will simply ignore this and cite you for their state's laws anyway and leave it up to YOU to deal with the appeal so you can explain it to a judge...they have enough things to worry about.