There is no active mechanism to enforce gun laws when crossing state lines (and there are often safe passage laws if you are just driving through without stoppi

There is no active mechanism to enforce gun laws when crossing state lines (and there are often safe passage laws if you are just driving through without stopping), but you can be charged if you are pulled over for another reason and the police see an illegal gun in your car. I imagine sugar tax enforcement would work similarly to the gun enforcement, not dedicated checkpoints for private cars (commercial trucks which already have checkpoints). You get pulled over for speeding, the police officer sees you have 18 cases of soda, and all of a sudden you get two fines.