California Code, Code of Civil Procedure - CCP § 715.040

(a) A registered process server may execute the writ of possession of real property as provided in subdivisions (a) and (b) of Section 715.020 if a proper writ of possession is delivered to the sheriff or marshal and that officer does not execute the writ as provided in subdivisions (a) and (b) of Section 715.020 within three days (Saturday, Sunday, and legal holidays excluded) from the day the writ is delivered to that officer. If the writ is not executed within that time, the levying officer shall upon request give the writ to the judgment creditor or to a registered process server designated by the judgment creditor.

(b) Within five days after executing the writ under this section, all of the following shall be filed with the levying officer:

(c) If the writ is executed by a registered process server, the levying officer shall perform all other duties under the writ and shall return the writ to the court.

(d) The fee for services of a registered process server under this section may, in the court's discretion, be allowed as a recoverable cost upon a motion pursuant to Section 685.080. If allowed, the amount of the fee to be allowed is governed by Section 1033.5.