He should have been using the international games as a showcase for his talents really. Underage International games are packed with scouts form all over Europe, if he has ambitions of playing at a professional level then playing for Ireland should have been put first by himself.
Anyway, as Pineapple Stu as said, Rules have been broken by Derry over this, i don't want to see any action taken but accept that rules have been broken. Jesus just count yourself lucky that he didn't come back injured like Gary Shaw did.