MPEG-LA asked the DOJ for clearance before they set up, since patent cartels of that type had been busted under anti-trust legislation in the past.
They made some concessions to the DOJ in order to be able to operate, which at least one licencee claims they've failed to honor. You can Google for the Nero AG vs MPEG-LA antitrust case for more info. (edit: a link, http://www.osnews.com/story/23346/Nero_Files_Antitrust_Case_...)
So it makes perfect sense for the DOJ to be involved. It's not just a patent dispute.
They made some concessions to the DOJ in order to be able to operate, which at least one licencee claims they've failed to honor. You can Google for the Nero AG vs MPEG-LA antitrust case for more info. (edit: a link, http://www.osnews.com/story/23346/Nero_Files_Antitrust_Case_...)
So it makes perfect sense for the DOJ to be involved. It's not just a patent dispute.