The counselor, social worker, and marriage and family therapist board shall establish a code of ethical practice for persons licensed under this chapter as licensed professional clinical counselors or licensed professional counselors. The board shall establish a code of ethical practice for persons licensed under this chapter as independent social workers or social workers, persons registered under this chapter as social work assistants, and persons licensed as independent marriage and family therapists or marriage and family therapists. The codes of ethical practice shall be established by adopting rules in accordance with Chapter 119 of the Revised Code. The codes of ethical practice shall define unprofessional conduct, which shall include engaging in a dual relationship with a client or former client, committing an act of sexual abuse, misconduct, or exploitation of a client or former client, and, except as permitted by law, violating client confidentiality. The codes of ethical practice may be based on any codes of ethical practice developed by national organizations representing the interests of those involved in professional counseling, social work, or marriage and family therapy. The board may establish standards in its codes of ethical practice that are more stringent than those established by national organizations.