Who Are The "People" Protected By The Second Amendment?

Does the right to keep and bear arms apply only to "law-abiding" citizens, and if so, then what's to prevent state or federal governments from prohibiting gun possession for anyone who's ever gotten a speeding ticket or smoked a joint (even in states where it's legal)? Who exactly fits under the Second Amendment's umbrella of protection for the right of "the people" to keep and bear arms? Those questions are at the heart of a case that could soon be heard by SCOTUS, and the ramifications of any Supreme Court decision are likely to have a major impact on the gun control debate going forward.