The government cannot demand anything. The well-regulated part is a justification clause.
Imagine if the 2A said this:
> "A well tailored suit, being necessary to a sharply dressed citizenry, the right of the people to keep and wear clothing, shall not be infringed."
Does this mean that the government now has a right to force dress codes on people so that their suits are well tailored?
Also justification clauses have been used in other contemporary laws too:
> Retrospective laws are highly injurious, oppressive and unjust. No such laws, therefore, should be made, either for the decision of civil causes, or the punishment of offences.
(From NH Ex Post Facto Article)
Does this mean that ONLY when the ex-post facto laws are injurious, oppressive and unjust, should that law be unconstitutional according to the NH constitution?