How would your state know you modified your vehicle, in order to not issue a registration? Sure, in sale, you sign a thing claiming "I have not modified, removed, or caused to be removed, any emissions devices or equipment"; but thats just a signature; doesn't mean anything, just sign it and move on. Are they planning on having cops pull people over to check for emissions equip?
I know some states do inspections of some sort every year/fee years; but that's the minority of states, and no idea what they actually inspect to get your registration.