If your ex-husband owes that much in child support, he should be on the lists maintained by DOR/CSE which reports to various law enforcement agencies, including customs, which should ensure that he would be picked up by police if he tries to re-enter the country.
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Attorney Molloy is correct. You should contact DOR and ask what enforcement remedies are being used in your case. DOR has a wide range of administrative remedies that can use against your ex-husband, you only need to ask for them to be enforced. You can contact DOR at 800-332-2733. Good luck!
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I just want to add to Attorney Molloy's succinct and correct assessment that you also may have options to seize assets if they are located in the United States. If you think this is possible, or that you may be able to find assets, you should speak to a lawyer about this.
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