Every provision of chapters 34 to 36, inclusive, of this title, shall be subject to amendment or repeal by any future session of the general assembly, provided that no such amendment or repeal shall diminish or annul, in any respect, any right acquired by a member or beneficiary under the provisions of chapters 34 to 36, inclusive, of this title or with respect to any fund derived from contributions made by members of the retirement system from its date of establishment.
T.C.A. § 8-3447