"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
The arguments about the meaning of the Second Amendment are near-continuous, even since DC v. Heller. Possibly the three most oft-repeated arguments invoked to weaken it are attempts to narrowly define the meaning of "arms", attempts to argue that "the People" actually means "the States" when used in the Second Amendment, and arguments that the prefatory militia clause, rather than being explanatory, is rather a condition, and that it is no longer true.
To get a clearer insight on this last, we can shortcut much argument by simply considering the original draft form of the relevant passage in the Bill of Rights recommended by the Virginia Ratifying Convention, in June 1778:
"That the people have a right to keep and bear arms; that a well-regulated militia, composed of the body of the people trained to arms, is the proper, natural, and safe defence of a free state; that standing armies, in time of peace, are dangerous to liberty, and therefore ought to be avoided, as far as the circumstances and protection of the community will admit; and that, in all cases, the military should be under strict subordination to, and governed by, the civil power."
It's pretty clear from reading this that the keep-and-bear clause stands on its own, and that rather than being a necessary condition for it, the militia clause is actually a benefit enabled by it. The draft then goes on to explain why a citizen militia is felt to be superior, in time of peace, to a standing army, but recognizes that this is not always possible by amending the qualifier "as far as the circumstances and protection of the community will admit". No such qualifier — indeed, no qualifier whatsoever — is amended to the keep-and-bear clause.
Any questions?