401k Plan wants me to Submit 'a Legal Document'
A divorce decree is an order by a court that can only be rescinded by a court. The court would need to issue another order rescinding the previous order. If a separation agreement is filed prior to a divorce decree, it will either be incorporated into the divorce decree or superceded by the divorce decree.
Generally, the only way to rescind a divorce decree is by filing an appeal with the court. Appealing a divorce decree has time limits, and due to the complicated nature of appeals, a local attorney who can review all the facts and circumstances involved should be consulted.