A bank which, on the effective date of this act, maintains or participates in a retirement plan or fund not contrary to law in effect at the time of the adoption of or any alteration of such plan or fund, is authorized to continue to maintain or participate in such plan or fund and it may alter such plan or fund from time to time in a manner not inconsistent with the provisions of this act.
N.J.S. § 17:9A-27.21