Cal. Health & Safety Code § 7116

Cremated remains may be scattered in areas where no local prohibition exists, provided that the cremated remains are not distinguishable to the public, are not in a container, and that the person who has control over disposition of the cremated remains has obtained written permission of the property owner or governing agency to scatter on the property. A state or local agency may adopt an ordinance, regulation, or policy, as appropriate, authorizing, consistent with this section, or specifically prohibiting, the scattering of cremated human remains on lands under the agency’s jurisdiction. The scattering of the cremated remains of more than one person in one location pursuant to this section shall not create a cemetery pursuant to Section 7003 or any other provision of law.