writes "In its last day of session, the Supreme Court has definitively clarified the meaning of the Second Amendment. The confusion is whether the Second Amendment allows merely for the existence of a state militia, or the private ownership of guns. This ruling is in response to a case regarding the 32-year-old Washington DC ban on guns."
This is one of the most-watched Supreme Court cases in a long time, and Wikipedia's page on the case
gives a good overview; the actual text of the decision
(PDF) runs to 157 pages, but the holding is summarized in the first three. There are certainly other aspects of the Second Amendment left unaddressed, however, so you can't go straight to the store for a recently made automatic rifle.