Green Party TD Patrick Costello has lost his challenge to Ireland's proposed ratification of the Comprehensive Economic Trade Agreement trade deal between the European Union and Canada.
Mr Costello had challenged the constitutionality of aspects of the deal in the High Court.
However the court this morning rejected his case and found that he had not established that ratification of the deal in the manner proposed would be unconstitutional.
The Dublin South-Central TD had claimed the deal should be put to the people in a referendum.
He said the ratification of the deal might have an impact on the State's ability to introduce regulation, particularly in relation to the environment.
Mr Costello also argued that because CETA allowed the State to be made liable for losses suffered by Canadian investors as a result of such regulation, it could have a "chilling effect" on the willingness of the State to introduce any such measures.
He added that CETA transferred part of the judicial powers of the State to tribunals established under the deal to resolve disputes between investors and States.
Because of this, he said, a vote of the people was required.
However, Ms Justice Nuala Butler found CETA did not entail an unconstitutional transfer of the State’s sovereignty.
She found it was an international agreement which did not have direct effect in Ireland and that tribunals established by CETA would not have jurisdiction to declare any provision of Irish law invalid.
Justice Butler also found that it was constitutionally appropriate and permissible for the State to ratify the agreement without a referendum.