SAN FRANCISCO —- The United States District Court for the Northern District of California announces today that Chief Judge Vaughn R. Walker will step down as chief judge effective December 31, 2010. Also, Chief Judge Walker notified President Obama by letter today that he will leave the court in February 2011.Chief Judge Walker has been a United States District Judge since February 5, 1990 and has served as chief judge of the court since September 1, 2004. Before becoming a federal judge, Chief Judge Walker was a litigation partner at the firm now known as Pillsbury Winthrop Shaw Pittman LLP. Upon leaving the federal bench, Chief Judge Walker plans to return to the private sector.In his letter to the President, Chief Judge Walker said: “Concluding twenty-one years of judicial service, I leave the bench with the highest respect and regard for the federal judiciary, its judges and their staff and the essential role they fulfill in our constitutional system.”By statute, United States district chief judges are selected based on a combination of age, seniority and experience and may serve in the post for a maximum of seven years. 28 USC § 136. By application of this statute, District Judge James Ware will assume the post of chief judge of the Northern District on January 1, 2011.