The Iowa example seems weird, but is because CH is in the middle of the EU, not an edge. So it is "objects" being "flown in directly" that are potentially leaving the confines of CH and going into the EU. Hence the bizarre example.
I understood why you used it. It is the same issue marijuana legalization in the US. EU has to police it just like neighboring states of Colorado.
Almost. But add the bit about the airport, that's key. In CO right now, anything that leaves CO had to be made in CO. They can't ship marijuana in or out. (But they can produce it, so that's nearly unlimited.) But in the CH example, stuff flies over the borders and into the middle, then is free to travel around. So the source objects could come from anywhere, not only be created inside CH.
They law may state they cannot ship in or out but there is nothing stopping the people from doing so. By plane or car. No stopping the law breakers. Just like the CH/EU situation.
The only people the EU will be hurting is the law abiding folks. Especially those in the town you mentioned above.
Again, I am not saying CH can not/should not increase their gun laws to match the EU. The CH just shouldn't have a fist in their face to force them to do it to keep an accord going.