Responsible gun owners have a duty to keep guns out of the hands of criminals. If you are forced to surrender your guns against your will make sure they are useless. Just in case they get lost on their way to be destroyed. For safety.
A dab of JB weld in the chamber should do the trick. Once the bolt closes, it ain't ever shooting again.
EDIT: To all the folks saying "Muh 1776!"... Only a small percentage of Americans went to war with the redcoats. A lot of people comply, for many reasons. This is for them, retailers especially, they can at least guarantee these guns don't go to Ukraine, Syria, ISIS, Gangbangers, etc.
This is really the advice? Comply, but disable your guns first?
Is there even a line that cannot be crossed anymore?
Losing your guns in a boating accident is way better.