No provision of this chapter generally and no provision of Code Section 47-20-50 in particular shall:

(1) Create or be construed to create a contractual right to a retirement benefit or a contractual right in the provisions of a retirement system law which does not exist independently of the provisions of this chapter; and

(2) Impair, alter, or diminish or be construed to impair, alter, or diminish a contractual right to a retirement benefit or a contractual right in the provisions of a retirement system law which exists independently of the provisions of this chapter.