Starke said:
The Five-Seven probably isn't actually illegal if you're in the States. But, I've always been under the impression that it only existed to allow FN to classify the P90 as an SMG.
EDIT: to put something in perspective, if you're firing airsoft BBs, the rounds its firing are actually larger than the Five-Seven's rounds.
The Five-Seven is perfectly legal in most states. However, there was some debate as to whether or not to allow them to be sold in the U.S. because they were/are too good at what they do - piercing things... Armored things.
I just use mine for targets. It's a PERFECT target pistol. It fires a small, fast round that is EXTREMELY accurate. The only problem that I have had with mine is that I knocked the front sight a little loose by trying to fit it into a universal holster that wasn't. I intend to carry it when I get my CCW permit, but it's not 100% perfect for that due to the problem of over-penetration. The hollow points help, but they are not a gurantee. Besides, I don't even know if I will be able to find a holster for it... The front sight is extra tall to accomodate a suppressor if so desired.