While the Second Amendment does apply to U.S. Citizens, it does not apply to undocumented/illegal immigrants. Illegals should not be purchasing guns anyway, if they are making such attempts, they are likely plotting unlawful activity, acts of terror, gang activity, using them in the act of smuggling or human trafficking or are otherwise up to no good. If an illegal is denied purchase of a firearm per NICS results, it should absolutely be reported to ICE. This should lead to automatic detention & subsequent deportation of said illegals. Any gun shops that are non-compliant should be raided & shut down by ICE. While I'm a hardcore supporter of the Second Amendment, it does not apply to illegal immigrants.