There is a case from the 70's I believe where a man in New York got a judgement against the former Soviet Union for $25000. When the Soviet Union failed to pay, he got a federal marshall and went to JFK and seized an IL62. The Soviet Union complained to the State Departement but the State Department told the Soviet Union that we have rule of law in the US and that they couldn't do any thing. Shortly, there after, the Soviet Union paid up.

I have heard of ground handling companies chaining up pushback trackers to foreign carrier airlines to force payment.