First, as the overwhelming majority of circuit decisions conclude, the text and history of the Second Amendment establish that it protects weapons possession and use only in connection with service in state-regulated militias. That conclusion is supported by United States v. Miller, 307 U.S. 174 (1939), in which this Court unanimously directed that the Second Amendment “must be interpreted and applied” in view of its “obvious purpose to assure the continuation and render possible the effectiveness of such [militia] forces.” Id. at 178. Second, even if there is a right to possess and use weapons unrelated to militia service, the Second Amendment restricts only federal interference with state-regulated militias and staterecognized gun rights. Legislation enacted by the District does not implicate the Amendment. Third, in any event, the District law at issue in this case does not infringe whatever right the Second Amendment could be read to protect, because it is eminently reasonable to permit private ownership of other types of weapons, including shotguns and rifles, but ban the easily concealed and uniquely dangerous modern handgun.The petition as a whole follows this template, with most of the argument making the traditional case for the militia-focused view of the Amendment. Interestingly, the petition cites none of the scholarship of scholars advocating the "individual right" interpretation of the Second Amendment.
On the merits, I count four just about certain votes to reverse (Stevens, Souter, Ginsburg, Breyer), one likely vote to reverse on the merits (Kennedy), two likely votes to affirm on the merits (Scalia, Thomas), one probably leaning towards affirming (Roberts), and one unknown (Alito). I put Alito in the unknown category because I suspect that his long experience as a prosecutor makes him more of a law-and-order conservative on this issue than his more ideologically conservative brethren. But who knows how this will all play out? Like the Fifth Circuit in the Emerson case, the Supreme Court (or individual Justices) could say that in general the Second Amendment protects an individual right but that this law is justified, either because DC is a federal enclave (unlikely if they've already adopted the individual right view, because then they will have rejected the state militia view) or (more likely), on the ground that handguns are more dangerous (because easily concealed and transported) than long guns.
There's enough uncertainty about the ultimate outcome of the case that even with four votes to reverse on the merits, it's not clear to me there will be four votes to grant cert. One or more of these four might "defensively deny," i.e., vote to deny cert for fear that taking the case would result in affirming, thereby taking a bad DC Circuit decision and making it the law of the land. However, the unmistakable circuit split means that any such qualms will likely be overcome and so I expect the Court---after calling for a response and for the views of the Solicitor General---will take the case.
While I'm making predictions, I'll also predict that the Court's decision, which will probably be issued some time in late June 2008, will instantly become an issue in the Presidential election, regardless of how the case is decided. That in turn, is likely to benefit the Republican candidate, because gun rights types tend to be more single-issue voters than gun control supporters.