(a) seems likely constitutional as it appears to only restrict those who are not the people inside the united states from bearing nukes. It is "an infringement" but not one of the ability of "the people" of the United States to keep and bear nukes.
(c) I would argue, from a strict reading of the constitution, is unconstitutional as it bans mere possession domestically of nukes. I could be misreading that section though. IMO there really should be constitutional amendment of the second to clearly ban nukes and possibly some other WMDs. As a bonus once all that stuff is spelled out it will give a lot less ammunition for people to hold the second amendment hostage by saying "well we have to interpret it creatively because we'll all be living on a radioactive sheet of glass if we don't."
note: entertainment and not legal advice
side note:
Domestically people designated to be "terrorists" can legally buy and be sold arms (see the terrorist screening center list and TSC no-fly list, the people on there can buy guns inside the US if not otherwise prohibited persons). That is someone on the terrorist list at the TSC can walk into a gun store and pass the background check no problem, and be sold a gun domestically.
