http://www.fnmfg.com/lawenf/57ammoinfo.htm
"BATF regulations: All components of this system are tightly regulated by BATF. The P90 (NFA, Class III weapon) can only be sold and registered to a law enforcement agency. The Five-seveN pistol is slightly different. The first sale, which requires the pistol to be legally imported into the US, requires the same procedure as the P90. A BATF Form 6 is needed which the chief or the second in command must sign. The pistol can then be removed from the Custom Bonded Warehouse and shipped to the agency. The ammunition is controlled in much the same manner, an approved BATF Form 6 is required then the ammunition can be shipped direct to the agency."