166.520.  Rulemaking authority. — Any rule or portion of a rule, as that term is defined in section 536.010, that is promulgated pursuant to sections 166.500 to 166.529 shall become effective only if it has been promulgated pursuant to the provisions of chapter 536.  All rulemaking authority delegated prior to August 28, 2004, is of no force and effect and repealed; however, nothing in this section shall be interpreted to repeal or affect the validity of any rule filed or adopted prior to August 28, 2004, if it fully complied with the provisions of chapter 536.  Sections 166.500 to 166.529 and chapter 536 are nonseverable and if any of the powers vested with the general assembly pursuant to chapter 536 to review, to delay the effective date, or to disapprove and annul a rule are subsequently held unconstitutional, then the grant of rulemaking authority and any rule proposed or adopted after August 28, 2004, shall be invalid and void.