A civil case initially assigned to a district judge may also
be reassigned to a magistrate judge if all parties consent to magistrate
judge jurisdiction. The parties should expect the district
judge to ask at the case management conference whether they
have considered consenting to a magistrate judge jurisdiction.
See: consenting to a magistrate judge's jurisdiction in the Northern District of Ca
http://www.cand.uscourts.gov/filelibrary/34/MagistrateJudgeBrochure-7-2011.pdf