The black guns you see were purchased and got through the border "before 1998" *cough**cough*.
Short of smuggling the guns in yourself you can't buy from outside of the country and if you get caught smuggling it's a heavy jail sentence (like federal offense) and fine.
Only way to get black guns that isn't illegal is to get AV'ed on this site and getting them through retailers if you want NIB or if you're willing to get used guns there's plenty available being listed by members in the Classifieds section.
You can direct any and all questions to your AV rep when you go there in person (after reading the FAQ's) if they have time to chat.
PS: Filling in your profile and location helps a lot.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE