Okla. Stat. tit. 40 § 160
As a matter of public policy and due to an overriding state interest, the Legislature hereby occupies and preempts the entire field of legislation in this state touching in any way mandated minimum wage and employee benefits regarding mandatory minimum number of vacation or sick leave days. Notwithstanding any exemption from state statutes previously allowed for certain municipalities pursuant to Section 1-101 of Title 11 of the Oklahoma Statutes, no municipality or other political subdivision of this state shall establish a mandatory minimum number of vacation or sick leave days, whether paid or unpaid, or a minimum wage rate which an employer would be required to pay or grant employees. Any existing or future ordinances, orders or regulations in this field, except as may be specifically provided in this section, are null and void.
The provisions of this section shall not affect the minimum number of vacation or sick leave days, whether paid or unpaid, authorized by a municipality for its employees as a benefit of employment.
Okla. Stat. tit. 40, § 160