Or at least every legal power or rule they might use
. I know that in some US states (they're standardizing, but still there's a wild profusion of state and local laws over here) double edgedness is specifically a factor. AFAIK, though there's rarely any trouble about this, it is illegal to buy, import (from anywhere, United State, or not), and maybe possess, a double-edged blade in California and Massachusetts (though AFAIK enforcement is sporadic and selective); every place that sells such mail-order seems to have a warning about these two states and some won't even ship such to them. The mail seems to me to be significantly safer/less minded than luggage taken with, at least USA-wise. Also, I don't think you'll get in any worse trouble over an edged weapon in the mail than having it stolen or owing a tariff (in USA they're known to come knocking at your door over some pills or ivory), so I have often just sweated it until the thing came, then been glad when it does, but a friend who got hit ONCE with the taxes says they were more than the item is worth and swears "Never Again [source country deleted before it's repeated
]!"