From http://www.camtc.org/faq.htm :
For anyone not certified by CAMTC, SB 731 makes it an unfair business practice for a person to use the titles "Certified Massage Therapist", "Certified Massage Practitioner", "CMT" or "CMP".
Massage practitioners who choose not to apply (or who do not qualify) for our certification are not prohibited from practicing in California, as what we offer is, by law, a voluntary certification. However, most professional massage therapists will want to have and use the CMT or CMP titles.
Ridiculous. Calling this a voluntary certification is pure sophistry.