How does Legal and physical Joint Custody Wok when one parent leaves the state without permission?

My husband and his ex have two children and joint legal and physical custody, ordered in SC. The ex took the two children and moved to Ohio with her brother and my husband wants them back here. Is there any way he can make her bring them back to SC where he can provide for them properly. His ex doesn't work, she gets a $410 welfare check a month, medical help for her and the children, and she receives $356 in food stamps per month. If they were here, the children would have a stable home, their two sisters, food, clothing and insurance from BMW where he works. She left SC without any agreement and without arranging any type of visitation, my husband has not seen these children since July 2007 because we cannot afford to go up there, well he can't get off work. He feels that she should bring them home because she left without making sure he could be an active part of their lives and he didn't agree to the move.