I understand that the student in question is being charged the non EU fee by Trinity College Dublin because under the admission requirements regulations of the college he does not qualify as an EU applicant.
The admission requirements regulations of TCD state that an EU application is one made by a person:
(a) who is permanently resident in the EU and who will have received full time post primary education in the EU for three of the five year immediately preceding admission, or who has worked full time in the EU for three years immediately preceding admission: or
(b) who holds a passport from an EU state and has received all his/her full time post primary education within the EU, or has received full time education in the EU for three of the five years immediately preceding admission.
Applications from children of EU Government officials living abroad are treated as EU applications. All other applications are considered to be non-EU applications.