I am just wondering, if say the IRS deems a foreign national, a non-resident alien liable for taxes and the person refuses to pay, What can the IRS do? I would guess that they would try to seize any assets you might have in the USA. However, for argument's sake, let say said person has no assets in USA at all. Will the IRS try to extradite you to the USA? Has there been a precedent for this?