Yes, a foreign creditor can force payment.  They can sue in their own country and "domesticate" a foreign judgment or they can bring suit in the US (if proper jurisdiction can be established).  Either way, your son will be on the hook financially if his creditor wins the case and obtains a judgment.Since he does not currently have any job or assets, there is little that they can do to him now.  However, judgments are good in MA for 20 years, so down the line this creditor can seize any non-exempt assets that your son has at that time, as well as garnish his wages, etc.  Again, right now there really isn't too much that they can do other than possibly make a negative notation on his credit report.Note:  Depending on the amount of the debt owed, this creditor may just be threatening legal action.  The fact is that enforcing a foreign judgment costs money and it may well not be worth it for them to to pursue the claim.