Okla. Stat. tit. 80, § 4.1

Jurisdiction shall be, and the same is hereby ceded to the United States over the tract of land comprised within the limits of the El Reno Federal Correctional Institution and El Reno Federal Prison Camp, an area about three thousand five hundred ninety-five (3,595) acres in Canadian County; provided, however, that the State of Oklahoma reserves concurrent jurisdiction to enforce the criminal laws of the State of Oklahoma within the said correctional institution and prison camp; and reserves the right to serve civil or criminal process within said correctional institution and prison camp in suits or prosecutions for or on account of rights acquired, obligations incurred, or crimes committed in said state but outside of said correctional institution and prison camp.