Missouri constitution
Article III: legislative department
Section 29

No law passed by the general assembly, except an appropriation act,
shall take effect until ninety days after the adjournment of the session in either oddnumbered
or even-numbered years at which it was enacted. However, in case of an
emergency which must be expressed in the preamble or in the body of the act, the general
assembly by a two-thirds vote of the members elected to each house, taken by yeas
and nays may otherwise direct; and further except that, if the general assembly recesses
for thirty days or more it may prescribe by joint resolution that laws previously passed
and not effective shall take effect ninety days from the beginning of the recess.