Proposes to amend the General Provisions Article of the Illinois Constitution. In a provision that specifies that membership in any pension or retirement system of the State, any unit of local government or school district, or any agency or instrumentality thereof shall be an enforceable contractual relationship, the benefits of which shall not be diminished or impaired, limits the benefits that are not subject to diminishment or impairment to accrued and payable benefits. Provides that nothing in the provision or in any other provision of the Illinois Constitution shall be construed to limit the power of the General Assembly to make changes to future benefit accruals or benefits not yet payable, including for existing members of any public pension or public retirement system. Effective upon being declared adopted.