Registration, mandatory inspection of firearms and frequent training were all essential to a well-regulated militia.

CNN: Put reason back in America's gun debate

The firearms used by a well-regulated militia, at the time the Second Amendment was written, were mostly long arms that, like a smaller stockpile of pistols, could discharge only once before they had to be reloaded.

NEWYORKER: Battleground America

To decide the case, the justices had to rule directly on the meaning of the Second Amendment, a provision with only 27 words: 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.

NPR: Supreme Court Strikes Down D.C. Handgun Ban