Mo. Rev. Stat. § 12.020: Jurisdiction given with reservations.

The jurisdiction of the state of Missouri in and over all land acquired as provided in section 12.010 is granted and ceded to the United States so long as the United States owns the land; except that there is reserved to the state of Missouri, unimpaired, full authority to serve and execute all process, civil and criminal, issued under the authority of the state within the lands or the buildings.