Judges are subject to many checks on their power. First, they only can rule on cases brought before their court, which requires two other parties to want a trial (including, in this case, the Justice Department). Also, unless they are in the Supreme Court, judges generally do not choose which cases they hear. Finally, and most significantly, they also are restricted by laws made by the legislature, precedent made by other judges and higher courts, the facts, juries (if the litigants wish to use them), principles of law, and appeals.