California Code, Public Contract Code - PCC § 22152

(a) All local public entities shall require all business, as defined in Section 12200, to certify in writing the minimum, if not exact, percentage of postconsumer materials in the products, materials, goods, or supplies, offered or sold. All contract provisions impeding the consideration of recycled products shall be deleted in favor of performance standards.

(b) With respect to printer or duplication cartridges that comply with the requirements of subdivision (e) of Section 12156, the certification required by this subdivision shall specify that the cartridges so comply.