The idea that the Second Amendment only guaranteed a state's, rather than an individual's, right to bear arms is known as the collective rights theory. To legal scholars who embrace that interpretation, it means that local, state and federal legislators have broad authority to regulate firearms, including who can own them, what types they can own and what they can do with them. (The opposing view is the individual right theory, which says that the Second Amendment prevents legislative bodies from prohibiting or restricting a person's possession of firearms) [source: Cornell].
This didn't become significant until 1934, when Congress — in an effort to stop violence by heavily armed criminal gangs — passed the National Firearms Act, requiring the registration and taxation of machine guns and certain other weapons [source: ATF]. Five years later, in United States v. Miller, the U.S. Supreme Court ruled in the case of two bank robbers who'd been charged with violating the act, "in the absence of any evidence tending to show that possession or use of a [sawed-off] shotgun ... has some reasonable relationship to the preservation or efficiency of a well regulated militia, we cannot say that the Second Amendment guarantees the right to keep and bear such an instrument" [sources: LOC, Frye ].
The Supreme Court's apparent embrace of the collective rights theory seemed to give Congress and the states wide leeway to regulate guns. That view didn't get much of a challenge for several decades. But then, in the late 1960s, amid fear of rising violence in cities and increasing racial strife, there was a surge in people wanting to arm themselves, particularly in conservative parts of the country.
By the late 1970s, the National Rifle Association, once primarily a sports shooting group, had morphed into an increasingly vocal force advocating the individual right to possess a firearm for protection. And the Republican Party, which in 1972 actually advocated gun control in its presidential platform, shifted to opposing firearms registration in 1980 [source: Waldman].
Those shifts started a debate on the meaning of the Second Amendment, which would culminate in a landmark 2008 U.S. Supreme Court case.