The NFL asked a federal judge Monday to keep its lockout in place. The league claims there are no legal grounds to stop it while accusing the players of trying to manipulate the law with a bogus antitrust lawsuit. The arguments were filed in federal court in St. Paul, Minn., where U.S. District Judge Susan Richard Nelson has scheduled an April 6 hearing on the players' bid to stop the lockout. Stopping the lockout, the NFL argued, would open all 32 teams up to additional antitrust claims even for working together to solve the labor fight.