Wrt British prisoners in the Republic.
A friend of mine's father was CO of the prison camp in the Curragh.
The prisoners had to sign out for their parole. The infamous case was of an officer who signed out then immediately returned as he had forgotten his gloves. On leaving for the second time he wasn't asked to sign out again and returned to the UK as he hadn't technically given his parole.
The Irish complained to the British who returned the offending officer.
There is an interesting site which details all of the aircraft that crashed or landed in the republic, many of which were returned.
Foreign Aircraft in Ireland 1939 - 1945
The first one was on the day hostilities were declared and three seaplanes accidentally landed in the republic. Two were at Skerries in the sea in front of my home and the third was in Howth.
What is very sad from the site is that many of the airman who were repatriated were killed later on in the war.
There are still wreckage on Irelands peaks.
I stayed in Rosslaire Monday and in front of my bedroom window is a plaque to the Viscount that crashed at Tuskar rock...the official line was fatigue, the unofficial was she was shot down by the RN.