Lawyers and laymen alike know vaguely that in McDonald v. Chicago, the Supreme Court found that state and local governments are, as the federal government is, limited by a constitutional individual right to bear arms.
But not everyone who approves of the end result is happy about how the 5-4 majority (or rather, 4-1-4 plurality) arrived to this conclusion. My good friend and legal scholar Josh Blackman explained a few months ago the two different paths the court could take: it could incorporate the Second Amendment against the states through the Fourteenth Amendment's due process clause, or it could use the Fourteenth Amendment's privileges or immunities clause.
The plurality went with the first option (Justice Clarence Thomas was the only one to go with the second). There has been and will be a lot of analysis of the implications of this decision, but the article Blackman co-wrote for the Washington Times explained and summarized the situation simply and clearly. Read it here.