"From Blackstone through the 19th-century cases, commentators and courts routinely explained that the right was not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose," wrote Scalia. "For example, the majority of the 19th-century courts to consider the question held that prohibitions on carrying concealed weapons were lawful under the Second Amendment or state analogues."
Nothing in the Heller ruling, he said, should be read 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."
Another "important limitation," explained Scalia, was contained in the justices' 1939 decision in Miller v. U.S. "Miller said, as we have explained, that the sorts of weapons protected were those 'in common use at the time.' We think that limitation is fairly supported by the historical tradition of prohibiting the carrying of 'dangerous and unusual weapons,' " he wrote.
Based on Miller, the Second Amendment does not protect weapons not typically possessed by law-abiding citizens for lawful purposes, such as short-barreled shotguns, he added.
The federal assault weapons ban, enacted in 1994, expired in 2004. That law had two bans: one on assault guns and another on high-capacity magazines holding more than 10 rounds of ammunition. Feinstein, the sponsor of the 1994 law, said her latest proposal will again ban both.
"Even before Heller, there were assault weapons bans challenged both on Second Amendment grounds and state right-to-bear arms provisions, and the bans were upheld," said Lowy of the Brady Center. "Connecticut, which has an assault weapon ban, does not ban high-capacity magazines."
But Kopel said the Second Amendment protects firearm accessories that pass the Heller test as well as firearms. He noted that New York Mayor Michael Bloomberg is advocating a ban on magazines holding more than 10 rounds.
"About three-quarters of all handguns sold in the U.S. today are semi-automatic as opposed to revolvers," said Kopel. "A great many modern semi-automatics have magazines which hold between 11 and 19 rounds. These would also seem to pass the Heller test because they are commonly used by law-abiding citizens for lawful purposes and extremely common."
Magazines of 30 to 40 rounds are also commonly possessed for rifles, he said, and 50-round magazines for rifles or 35 rounds for handguns also are "overwhelmingly" possessed by law-abiding citizens for lawful purposes, although not as "ubiquitous."
The language in Miller about "commonly used by law-abiding citizens for lawful purposes," is not entirely clear, acknowledged Kopel. Must the weapon be popular and commonly used by law-abiding citizens for lawful purposes, or just mainly used for lawful purposes, he said. But he said he would argue that all of the different magazine rounds pass the Heller test.