27 CFR §478.120

1. (a)General. A nonimmigrant alien temporarily importing or bringing firearms or ammunition into the United States for lawful hunting or sporting purposes must first obtain an approved ATF Form 6NIA (5330.3D).
2. (b)Aliens admitted to the United States under a nonimmigrant visa.
   1. (1)Any alien lawfully admitted to the United States under a nonimmigrant visa who completes an ATF Form 6NIA to import firearms or ammunition into the United States, or any licensee who completes an ATF Form 6 to import firearms or ammunition for such nonimmigrant alien, must attach applicable documentation to the Form 6NIA or Form 6 establishing the nonimmigrant alien falls within an exception specified in 18 U.S.C. 922(y)(2) (e.g., a hunting license or permit lawfully issued in the United States) or has obtained a waiver as specified in 18 U.S.C. 922(y)(3).
   2. (2)Aliens admitted to the United States under a nonimmigrant visa importing or bringing firearms or ammunition into the United States must provide the United States Customs and Border Protection with applicable documentation (e.g., a hunting license or permit lawfully issued in the United States) establishing the nonimmigrant alien falls within an exception specified in 18 U.S.C. 922(y)(2) or has obtained a waiver as specified in 18 U.S.C. 922(y)(3) before the firearm or ammunition may be imported. This provision applies in all cases, whether or not a Form 6 is needed to bring the firearms or ammunition into the United States.