Mo. Rev. Stat. § 337.325: Limitation on practice.

A licensed behavior analyst, licensed assistant behavior analyst, provisionally licensed behavior analyst, provisionally licensed assistant behavior analyst, temporary licensed behavior analyst and temporary licensed assistant behavior analyst shall limit his or her practice to demonstrated areas of competence as documented by relevant professional education, training, or experience. A licensed behavior analyst, licensed assistant behavior analyst, provisionally licensed behavior analyst, provisionally licensed assistant behavior analyst, temporary licensed behavior analyst and temporary licensed assistant behavior analyst trained in one area shall not practice in another area without obtaining additional relevant professional education, training, and experience.