Secondly, if there are children involved, the filing of a divorce case automatically prevents either party from moving the children to another state. In order to move with children to another state, either during or after a divorce case, you will be required to seek approval from the Court.
Finally, if moving to another city or county in the state of Illinois will not be in the best interests of the children, such as a dangerous neighborhood, or a threat to the children's well being or education, the other parent can petition the court to either prevent the move, modify any visitation order which may be in place, deem the other parent the primary residential parent, or give the other party sole custody. This is determined on a case by case basis, and it is very possible that the court will approve such a move if it serves the best interests of a the child involved.
Many divorce cases in Illinois involve spouses that try to "bully" or control the other party with threats of litigation if a party moves to another city of county. If you find yourself in such a situation, you should contact an attorney immediately to explain your options.