The Supreme Court has begun hearing an appeal by the State against a recent High Court ruling that restricts the capacity of Oireachtas investigations.
Last November, the High Court ruled that Oireachtas inquiries cannot make "findings of fact or expressions of opinion" that damage the good name of citizens who are not TDs or senators.
The landmark judgement effectively cancelled new powers given to Oireachtas committees to compel the attendance of witnesses and to force the production of documents.
In his opening submission for the State, Attorney General Mr Michael McDowell told the court that members of the Oireachteas were "duty-bound to protect and vindicate the rights of the person and as such were entitled to exercise the executive powers of the State in that regard".
Mr McDowell said this function could not be carried out in a "sealed box". He said the right of committees to embark on inquiries of public concern entitled members to examine the full "facts of the matter".
Contrary to the recent High Court ruling Mr McDowell said the judgment impeded members of the Oireachtas from carrying out its constitutional function of defending the rights of the person.
The hearing continues this afternoon.