Cal. Health & Safety Code § 8391

A reduction facility shall not make or enforce rules requiring that human remains be placed in a casket before reduction, nor shall a reduction facility refuse to accept human remains for reduction for the reason that they are not in a casket. A director, officer, agent, or representative of a reduction facility who violates this section is guilty of a misdemeanor. This section does not prohibit a facility from requiring some type of container or disposal unit.