Merscorp Inc., operator of the electronic-registration system that contains about half of all U.S. home mortgages, has no right to transfer the mortgages under its membership rules, a judge said. U.S. Bankruptcy Judge Robert E. Grossman in Central Islip, New York, in a decision he said he knew would have a “significant impact,” wrote that the membership rules of the company’s Mortgage Electronic Registration Systems, or MERS, don’t make it an agent of the banks that own the mortgages. “MERS’s theory that it can act as a ‘common agent’ for undisclosed principals is not supported by the law,” Grossman wrote in a Feb. 10 opinion. “MERS did not have authority, as ‘nominee’ or agent, to assign the mortgage absent a showing that it was given specific written directions by its principal.”