The defendants claimed that Chinese law compelled them to form a cartel to sell vitamin C, and the Chinese government even hired Sidley Austin to support that argument. But the companies still can't escape class action litigation over the alleged price-fixing, a Brooklyn federal judge ruled Tuesday.

A federal judge in Brooklyn agreed Thursday to certify classes of direct and indirect purchasers in a set of suits accusing four Chinese manufacturers of joining a cartel to fix prices for vitamin C. The litigation has drawn a rare U.S. court appearance by the Chinese government, which hired Sidley Austin to back the companies' defense.

After getting sued for patent infringement by a non-practicing entity called Oasis Research, EMC could have settled, like most of its co-defendants. Instead, the company filed an appeal with the Federal Circuit and won a ruling that limits the ability of patentholders to name multiple defendants in the same complaint. Now EMC is heading back to the Federal Circuit, seeking a ruling that could ease the way for more cases to be transferred out of the plaintiff-friendly Eastern District of Texas.