Hughes Aircraft Co. v. United States ex rel. Schumer
In Hughes Aircraft Co. v. United States ex rel. Schumer, 520 U.S. 939, 951 (1997), the U.S. Supreme Court held that a statute "that creates jurisdiction where none previously existed" is "as much subject to our presumption against retroactivity as any other." 
Writing for a unanimous Court, Justice Clarence Thomas held that whistleblower's qui tam action under the False Claims Act must be dismissed because it was based on information or evidence the government already had when the action was filed.