Sec. 17963. (1) The board shall promulgate rules to create a code of professional ethics. (2) A licensee shall make a written referral of a client to an appropriate health professional if the client's physical or medical condition appears to constitute a contraindication for massage therapy. (3) The board and department shall not, by rule or otherwise, restrict the right of a licensee to participate in and become a member of any nationally recognized trade or professional association.