Any rule or portion of a rule, as that term is defined in section 536.010, that is promulgated to administer and enforce sections 334.735 to 334.749, shall become effective only if the agency has fully complied with all of the requirements of chapter 536, including but not limited to, section 536.028, if applicable, after August 28, 1998. All rulemaking authority delegated prior to August 28, 1998, is of no force and effect and repealed as of August 28, 1998, however nothing in this act^* shall be interpreted to repeal or affect the validity of any rule adopted and promulgated prior to August 28, 1998. If the provisions of section 536.028 apply, the provisions of this section are nonseverable and if any of the powers vested with the general assembly pursuant to section 536.028 to review, to delay the effective date, or to disapprove and annul a rule or portion of a rule are held unconstitutional or invalid, the purported grant of rulemaking authority and any rule so proposed and contained in the order of rulemaking shall be invalid and void, except that nothing in this act^* shall affect the validity of any rule adopted and promulgated prior to August 28, 1998.