California Code, Labor Code - LAB § 1151

(a) The board, or its duly authorized agents or agencies, shall at all reasonable times have access to, for the purpose of examination, and the right to copy, any evidence of any person being investigated or proceeded against that relates to any matter under investigation or in question.  The members of the board or their designees or their duly authorized agents shall have the right of free access to all places of labor.  The board, or any member thereof, shall upon application of any party to such proceedings, forthwith issue to such party subpoenas requiring the attendance and testimony of witnesses or the production of any evidence in such proceeding or investigation requested in such application.  Within five days after the service of a subpoena on any person requiring the production of any evidence in his possession or under his control, such person may petition the board to revoke, and the board shall revoke, such subpoena if in its opinion the evidence whose production is required does not relate to any matter under investigation, or any matter in question in such proceedings, or if in its opinion such subpoena does not describe with sufficient particularity the evidence whose production is required.  Any member of the board, or any agent or agency designated by the board for such purposes, may administer oaths and affirmations, examine witnesses, and receive evidence.  Such attendance of witnesses and the production of such evidence may be required from any place in the state at any designated place of hearing.

(b) In case of contumacy or refusal to obey a subpoena issued to any person, any superior court in any county within the jurisdiction of which the inquiry is carried on, or within the jurisdiction of which such person allegedly guilty of contumacy or refusal to obey is found or resides or transacts business, shall, upon application by the board, have jurisdiction to issue to such person an order requiring such person to appear before the board, its member, agent, or agency, there to produce evidence if so ordered, or there to give testimony touching the matter under investigation or in question.  Any failure to obey such order of the court may be punished by such court as a contempt thereof.