Read the carriage of contract. That is the document concerning legality of transporting other people's property. It handles the examples you are throwing out.
It is not seized and destroyed. It is either held for the shipper to come pickup at their own expense as they don't have a valid shipping contract (because they didn't read the small print carriage of contract). If it made it into the shipment system and moved it is turned over to the proper authorities as the shipper violated the law and didn't read the fine print. If they choose not to do so in the time allotted by law it is disposed of by UPS or the proper authorities.
Same thing for any dangerous good/hazmat. Ever seen a hazmat response team from the fire dept remove an unauthorized package that some stupid driver picked up rather than argue with the customer about?
Guns are considered dangerous goods and governed by UPS dangerous goods contract. They are allowed in the system by shippers that follow the contract. Not allowed by those that don't. Simple as that.
Guns or firearms are
not considered
(dangerous goods)..
Before this newest mandate they were shipped off counters via
next day air..the reason was to get them to their destination as soon as possible, they were segregated and treated as a high value package. This service level requirement also was needed in order to prevent thief.
They had to be going to a licensed gun broker for transfer or repair, not person to person.
The manufacturer’s firearm returns can go second day air and
are permitted in our system for delivery. It makes sense because most of the returns are due to some design issues that have a ton of liability involved.
If a firearm ends up missing in our system law enforcement has to be called in and an investigation started. Still remember an incident when some part timers or temps were stealing a bunch of guns out of a trailer just before they were delivered to a large gun shop. I do not who was running LP at the location but it was far too easy for these kids to get them off the property.