People who don't trust you are not to be trusted
This item is a cross between a super-soaker and a fly-swatter. It shoots a small quantity of table salt to down pesky flies.
The highlighted text says, "This item cannot be shipped to your selected location."
That location would be, of course, California.
Note that Amazon does not sell guns. Not real guns. Never did.
So somebody (*cough*kamalaharris*cough*) must have put the kibosh on wing-shooting musca domestica, for their own nefarious reasons.
[Edit, 20 September 2017: Apparently it is just an Amazon ban. Californians can order direct from the manufacturer. I could even get one from the local ACE Hardware. So, 'sup wi'dat, Amazon? ]