Spotting a series of complicated choice-of-law questions about multistate regulation of group insurance policies that should have been addressed when ruling on Continental Casualty Co.’s motion for judgment on the pleadings — in a case where Carlton Gunn sued in Chicago alleging breach of contract and fraud involving premium increases under a master policy his employer received in the District of Columbia, and Continental invoked the filed-rate doctrine as a defense based on approval for the increases from the …