Mo. Rev. Stat. § 441.040
If any tenant violates the provisions of section 441.020 or 441.030, the landlord, or person holding under the landlord, after giving ten days' notice to vacate the premises, shall have a right to reenter the premises and take possession of the premises, or to oust the tenant, subtenant or undertenant of any person on the premises with the permission of the lessee, sublessee or underlessee by the procedure specified by law. The landlord shall have the burden to prove that the premises were being used for the illegal possession, sale or distribution of controlled substances under a petition filed for that reason, but the landlord shall not be liable for any damages resulting from the landlord's reliance on written notification to the landlord by a law enforcement authority that the premises are being used for the illegal conduct described in section 441.020.
§ 441.040, RSMo
RSMo 1939 § 2968, A.L. 1997 H.B. 361