If you were granted sole custody and he has no visitation rights per that same order, then he could be charged with "interference with custody of child."  Even though not exactly the same as kidnapping, it is a very similar offense which is a felony in Pennsylvania.  Many people do refer to this as "parental kidnapping."  This is a criminal remedy.  If he took the child, you would also be able to pursue interstate enforcement actions since Pennsylvania participates in interstate agreements to work with other states for the return of children.