So a Ninth Circuit panel, by a 2-1 vote, just struck down the broad California restriction on carrying guns in public. What now?
1. The defendants might well ask the Ninth Circuit en banc to rehear the case. If a majority of the sitting Ninth Circuit judges agrees with such a request, then the case will be reheard by 11 judges of the Ninth Circuit — Chief Judge Kozinski, plus 10 other randomly selected judges. (In theory, it’s also possible that the Ninth Circuit could rehear the case with all the active judges participating, but that has never happened and is unlikely to happen now.)
2. Whoever wins, it seems likely that the losing side will “petition for certiorari,” i.e., ask the U.S. Supreme Court to consider the matter. It’s possible that the losing side might choose not to file such a petition — Illinois didn’t challenge the Seventh Circuit’s decision upholding the right to carry guns, but instead implemented a shall-issue concealed carry licensing scheme. But it seems likely that a petition would be filed.
3. If a petition is filed, the Supreme Court is likely to hear the case. It has no legal obligation to do so, but there’s a solid split among federal circuit courts and state supreme courts on the issue (regardless of whether the Ninth Circuit reverses this panel decision en banc), and such a split is often seen by the Court as a reason to step in and resolve the matter. This is the sort of federal constitutional question that should be resolved by the Justices for the whole country, rather than having the same constitutional amendment being interpreted differently in different federal circuits.
[UPDATE: As Daniel Schmutter pointed out, it's also possible that the Supreme Court will grant certiorari before then in the Third Circuit right-to-carry case, which involves much the same issue, Drake v. Filko. If so, then the Court will either grant in the Ninth Circuit case and consolidate the two, or it can hold on to the petition in the Ninth Circuit case pending the result in Drake, and -- if the Drake decision changes the result for the Ninth Circuit case -- send the case back down for further consideration in light of the Drake decision. In any event, whether the Court grants Drake or this case, it would likely decide the Second Amendment right-to-carry question.]
4. How the Court will decide the question, if it does decide it, is hard to predict. It seems likely that, if no Justices leave the Court between now and then, a right to carry guns in public (in some form) would be upheld — a good deal of the language and reasoning of D.C. v. Heller points in that direction. But it’s hard to be certain.