They need only a copy of his conviction order and sentence, arrest him, then carry out teh sentence, He could of course be whisked off to israel by mossad , who could ask the death order be recognized in ISrael courts and sentence carried out. Simple no. Let him swing if the evidence is solid.
Policeman killed by blast in Bahrain village, interior ministry (Reuters)
from the article: Nazi war criminal found ‘alive and well’ in Hungary