Suing in Chicago after buying a house in New Jersey that was offered through the local Multiple Listing Service, Judah Leeder alleged that the National Association of Realtors and seven other defendants violated federal antitrust law by conspiring to artificially inflate commissions for buyer-brokers. But the defendants were protected by a brick wall — the indirect purchaser rule established by Illinois Brick Co. v. Illinois, 431 U.S. 720 (1977).The “bright-line” Illinois Brick rule “authorizes suits by direct purchasers …