My ex-spouse won't follow the court's order. What can I do?
Any violation of the court's order may be addressed through enforcement. This will include a failure to pay child support on time or at all, a failure to allow visitation or a failure to return a child at the end of visitation. In most states, an order may be enforced by a finding of contempt, which can include time in jail, fines, the award of attorney fees, or a requirement that a bond be posted.
It is also a general rule that child support and visitation have nothing to do with one another.
Therefore, if your former spouse refuses to pay child support, your remedy is a motion for Enforcement. You should not take matters into your own hands and withhold the child.