right. if you are driving a car registered in a single plate state (New Mexico, lets say) through a Double plate state (like MN) MN can not ticket you for only having one plate.
but, i'm not sure if say WI (also double plate) can ticket me for not having both my MN plates displayed.
vehicle equipment laws apply to the registered state. i can't tint my front windows or than i think 50% in MN, (legally, of course) but i can Drive to CA and get limo black (i think that's legal out there, right?) i won't have to worry about a ticket in Cali, but i bet i'll be getting a ticket not too long after i'm back in MN!
That sounds like you've heard of my wife's Nebraska speeding tickets!