Okla. Stat. tit. 59 § 858-726
An Oklahoma certified real estate appraiser must comply with the current edition of the Uniform Standards of Professional Appraisal Practice, as promulgated by the Appraisal Standards Board of the Appraisal Foundation when involved in a federally related transaction or a real estate-related financial transaction of the agencies, instrumentalities and federally recognized entities as defined and recognized by the Financial Institutions Reform, Recovery, and Enforcement Act of 1989, or when both the appraiser and user of appraisal services agree in writing that the work product is an appraisal, or when a written appraisal states that it is in compliance with the Uniform Standards of Professional Appraisal Practice.
Okla. Stat. tit. 59, § 858-726