California Code, Code of Civil Procedure - CCP § 1987.5

The service of a subpoena duces tecum is invalid unless at the time of such service a copy of the affidavit upon which the subpoena is based is served on the person served with the subpoena. In the case of a subpoena duces tecum which requires appearance and the production of matters and things at the taking of a deposition, the subpoena shall not be valid unless a copy of the affidavit upon which the subpoena is based and the designation of the materials to be produced, as set forth in the subpoena, is attached to the notice of taking the deposition served upon each party or its attorney as provided in Chapter 3 (commencing with Section 2002) and in Title 4 (commencing with Section 2016.010). If matters and things are produced pursuant to a subpoena duces tecum in violation of this section, any other party to the action may file a motion for, and the court may grant, an order providing appropriate relief, including, but not limited to, exclusion of the evidence affected by the violation, a retaking of the deposition notwithstanding any other limitation on discovery proceedings, or a continuance. The party causing the subpoena to be served shall retain the original affidavit until final judgment in the action, and shall file the affidavit with the court only upon reasonable request by any party or witness affected thereby. This section does not apply to deposition subpoenas commanding only the production of business records for copying under Article 4 (commencing with Section 2020.410) of Chapter 6 of Title 4.