...a judge should not initiate, permit, or consider ex parte communications or consider other communications concerning a pending or impending matter that are made outside the presence of the parties or their lawyers. If a judge receives an unauthorized ex parte communication bearing on the substance of a matter, the judge should promptly notify the parties of the subject matter of the communication and allow the parties an opportunity to respond, if requested.

http://www.uscourts.gov/judges-judgeships/code-conduct-united-states-judges