On August 14th, a panel of the US Court of Appeals for the 9th Circuit ruled 2-1 that magazines capable of holding more than 10 rounds of ammunition are indeed protected by the 2nd Amendment. As such, California's ban on the possession of these common items has been found unconstitional by the court. We welcome and agree with the majority opinion. California can seek rehearing en banc before a panel of 11 judges in the 9th Circuit and/or file a petition for certiorari before the United States Supreme Court.
You can read the opinion in Duncan v Becerra HERE