10. Until such a time as it's reviewed by a later Court decision.
Which is likely if the court is less conservative in coming years with the likely retirement of some members and appointment of others by a Democratic president. For almost 70 years the controlling decision was US v Miller, 1939, which endorsed the collective right view; there's not any reason to think that this may not be the case again, especially if the composition of the court changes. And no, the Second Amendment isn't "about individual self-defence"; see "well-regulated militia". See also: http://www.tnr.com/article/books/defense-looseness and http://www.nytimes.com/2008/10/21/washington/21guns.html?_r=2&hp&oref=slogin& (Scalia's legal reasoning has been criticised from the right as well as the left).