If the underlying reason behind your ex’s willingness to relinquish custody has changed, she might want to revoke her decision to step aside as the custodial parent. She may have had a mental health issue or a substance abuse problem that she has now successfully defeated. However, this is generally not a sufficient reason for a court to overturn an existing custody arrangement. Your ex would not only have to prove that circumstances have changed and she's now a good parent, but she would simultaneously have to prove that something has occurred to make you a bad parent. Unless your own life has changed so dramatically that your home is no longer safe for your children, this might be very difficult for her to accomplish.
Your ex must file a post-judgment or post-decree motion with the court, advising that she wants to change the custody terms of your decree. She must usually include a written affidavit or certification with the motion, explaining why she wants the change. This will not automatically change your decree. In most jurisdictions, a judge will review her paperwork and schedule a hearing. Because changing custody is a far more serious issue than other post-judgment issues, such as recalculating child support, most courts will not make such a decision at the motion hearing. In all likelihood, the judge will use the occasion of the motion hearing to order a plenary hearing. A plenary hearing is the same as a divorce trial, but it occurs after the divorce is final. Both you and your ex can call witnesses, testify on your own behalf and offer documented evidence to the judge.
Best Interests of the Children
After reviewing all evidence and listening to testimony during a plenary hearing, the judge will base his decision on the best interests of your children, not on the validity of your ex’s desire to change custody. Courts usually do not believe it is in children’s best interests to suddenly uproot them from the home of their primary caretaker. Judges generally give a lot of weight to existing custody orders and won’t radically change them unless something very significant has taken place to make the old arrangement unworkable. The benefits of changing custody must be greater than the stress such a change would cause your children. Many state courts will also consider the children’s wishes, especially if they want their living arrangement to remain as-is. Courts give more weight to children’s preferences when they’re older.
Because you already have an existing custody order in the form of your divorce decree, your best defense is that nothing has changed since your ex gave up custody, so there’s no reason to uproot your children. However, a plenary hearing is usually a complex and lengthy legal procedure, so you might want to hire an attorney to help you make this case. If you don’t believe you ex’s circumstances have changed since she ceded custody, an attorney can help you gather evidence to prove that. He can present it to the court through document exhibits and witness testimony.