Your options are to serve the "ex" with an order to show cause for contempt of a court order since the county and state in this country where you reside have jurisdiction over the matter.If the "ex" has assets in this country then you can levy upon such for satisfaction of back child support. If not, then there really is nothing you can do unfortunately due to the fact that he resides in a country where there is no reciprocal agreement with this country concerning child support.