In the event that the Legislature takes appropriate action to terminate the plan, or in the event of a partial termination of the plan, all amounts shall be allocated in accordance with the provisions hereof and the accrued benefit, to the extent funded as of such date, of each affected member shall become fully vested and shall not thereafter be subject to forfeiture. However, members who were not fully vested at the time they received a complete distribution of their vested benefits prior to the date of termination, shall not become entitled to any additional vested benefits on account of plan termination. The preceding sentence does not apply to members affected by a partial termination by operation of law. Upon full termination of the plan, the county shall direct the distribution of the assets in the trust fund to the members. In such case, the trustee shall distribute the assets to the remaining members in the plan and to retired members in cash or through the purchase of irrevocable deferred commitments from an insurer, subject to provision for expenses of administration or liquidation. Such distributions shall be allocated in such order as set forth by the Legislature, or by the pension board to the extent the pension board receives such authorization, to the extent of the sufficiency of such assets, basing such allocation on the accrued benefit for each such member at the date of termination of the plan.