See
Argentina With a judgement from a New York court,an American fund holding Argentinian sovereign bonds in default got a court order to impound an Argentinian frigate visiting Ghana.
Should Ireland default as looks inevitable unless the electorate puts up with decades of economic stagnation and emigration,the semistates and the government should have a plan to immediately liquidate and repatriate all foreign assets. An interesting point is whether virtually nationalised banks would count as state assets subject to seizures?