Miss. Code Ann. § 25-11-301

There is hereby established and placed under the management of the Board of Trustees of the Public Employees’ Retirement System of Mississippi a supplemental legislative retirement plan for the purpose of providing supplemental retirement allowances and other benefits under the provisions of this article for elected members of the State Legislature and the President of the Senate and their beneficiaries. The retirement plan provided by this article shall go into operation on July 1, 1989, when contributions by members shall begin and benefits shall become payable. This retirement plan is designed to supplement and is in addition to the provisions of Section 25-11-1 et seq. Under the terms of this article, the members of the State Legislature and the President of the Senate shall retain all social security benefits under Article 1 and additional state retirement and disability benefits under Article 3 of the Public Employees’ Retirement Law of 1952, as amended. This article is a supplement to those sections, and is designed to provide more benefits for members of the State Legislature and the President of the Senate by reason of their service to the state.