Concerning the Second Amendment

The Second Amendment is an individual right intimately tied to the natural right of self-defense.

District of Columbia v. Heller, 554 U.S. 570 (2008), in the majority opinion written by Justice Antonin Scalia:

"Like most rights, the Second Amendment right is not unlimited. It is not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose: For example, concealed weapons prohibitions have been upheld under the Amendment or state analogues. The Court’s opinion should not be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms. Miller’s holding that the sorts of weapons protected are those “in common use at the time” finds support in the historical tradition of prohibiting the carrying of dangerous and unusual weapons." 

Also,

"The handgun ban and the trigger-lock requirement (as applied to self-defense) violate the Second Amendment. The District’s total ban on handgun possession in the home amounts to a prohibition on an entire class of “arms” that Americans overwhelmingly choose for the lawful purpose of self-defense. Under any of the standards of scrutiny the Court has applied to enumerated constitutional rights, this prohibition – in the place where the importance of the lawful defense of self, family, and property is most acute – would fail constitutional muster. Similarly, the requirement that any lawful firearm in the home be disassembled or bound by a trigger lock makes it impossible for citizens to use arms for the core lawful purpose of self-defense and is hence unconstitutional."

And,

"[T]he conception of the militia at the time of the Second Amendment’s ratification was the body of all citizens capable of military service, who would bring the sorts of lawful weapons that they possessed at home."

 Thus, the Second Amendment was found to not apply to machine guns.

This is basically what rational liberals argue. They do not argue for the confiscation of all firearms. That would not only be silly, but unworkable. Visions of federal or U.N. soldiers going around collecting everyone's arms are pure fantasy and scaremongering. What they ask for is reasonable protections to keep guns out of the hands of those people who should not have them, protections which would include licensing and background checks (no gun show loophole), and restrictions on the owning of weapons of mass murder. The Second Amendment certainly does not give the right to own missiles or bioweapons. States are also given leeway to levy laws such as those concerning the carrying of concealed weapons and concerning the commercial sale of weapons.