Okla. Stat. tit. 40, § 553

A. The Standards for Workplace Drug and Alcohol Testing Act shall not be construed as requiring or encouraging employers to conduct drug or alcohol testing. B. Except as provided in subsection C of this section, employers who choose to conduct drug or alcohol testing of job applicants or persons employed in this state shall be governed by the provisions of this act and the rules promulgated pursuant thereto. C. Drug or alcohol testing required by and conducted pursuant to federal law or regulation shall be exempt from the provisions of the Standards for Workplace Drug and Alcohol Testing Act and the rules promulgated pursuant thereto. D. This act shall not be construed as preventing the negotiation of collective bargaining agreements that provide greater protection to employees or applicants than is provided by this act.