Marital separation agreements or settlement agreements, when incorporated in a divorce decree, have the force of a court order.
Willful violation of a court order is contempt of court. When the court orders something, the parties are expected to comply with those orders.
In a divorce, you often have orders stated in the final decree or judgment regarding, but not limited to, property distribution, debt distribution, spousal support, custody, child support, visitation (parenting time), and retirement accounts.
See Order, Order of the Court.