The European Convention on Extradition Order 1990

Article 9

The Government of the Grand Duchy of Luxembourg will not grant extradition if it is satisfied that final judgment for the offence for which extradition is requested has been passed on the person claimed by the competent authorities of a third State and, in the event of conviction for that offence, the convicted person is serving his sentence, has already served it or has been dispensed from serving it.