The European Court of Justice has ruled that bodies like the Workplace Relations Commission are entitled to disregard Irish law if it conflicts with European law - and that such a power is not restricted to the courts of law.
The ruling potentially boosts the powers not just of the WRC but of similar bodies charged with the enforcement of European Union law.
The ruling by the Grand Chamber of 15 judges examined the case of three men who were refused permission to join An Garda Síochána on the basis that they were over 35 - the maximum age set for recruitment by law.
Ronald Boyle, Gerald Cotter and Brian Fitzpatrick argued at the Equality Tribunal that setting a maximum age for recruitment to the force constituted discrimination prohibited by EU Directive 2000/78 and provisions of Irish law transposing that directive.
However, the Minister for Justice and Equality challenged the jurisdiction of the Equality Tribunal, arguing that only courts established under the Constitution - such as the High Court, the Court of Appeal and the Supreme Court - had the power to decide whether to disapply or disregard a provision of national law.
When the Equality Tribunal said it would consider the case, including the jurisdictional issue, the minister sought a High Court order prohibiting the tribunal from "acting in a manner contrary to law".
The High Court barred the tribunal from ruling on the Boyle case as it lacked jurisdiction to adopt a legally binding decision concluding that a national law was incompatible with EU law - as that power was reserved to the High Court under Article 34 of the Constitution.
The Equality Tribunal then launched a further appeal to the Supreme Court, which in turn referred a query to the ECJ.
The Supreme Court asked whether a national body established by law to ensure enforcement of EU law in a particular area - in this case equality legislation - must be able to disapply or ignore a rule of national law that is contrary to European law.
The ECJ Grand Chamber ruled that the WRC must have the power to disregard a national law that conflicts with EU law.
It drew a distinction between the High Court power to strike down a provision of law so that it is no longer valid for any purpose, and the WRC power in a specific case to disapply a national law that conflicts with EU law.
It found that the duty to give primacy to EU law is owed not only by national courts, but also "...by all organs of the State - including administrative authorities - called upon, with the exercise of their respective powers, to apply EU law".
The ECJ notes that the Irish legislature chose to confer the specific power of ensuring compliance with EU equality legislation on the WRC.
Against that background, it says that if the WRC has a dispute before it, the primacy of EU law requires it to provide the legal protection which individuals derive from EU law - and to ensure that EU law is fully effective - including, where necessary, disapplying any provision of national legislation that may be contrary to it.
It stated that it would be contradictory if an individual could rely on a provision of EU law in a particular area before a body on whom national law had conferred jurisdiction, but that the body would have no obligation to apply those provisions by refraining from applying provisions of national law conflicting with them.
Employment law sources described the ruling as a "landmark" decision which was "stunning".
They said it was particularly significant, given that the ECJ had overruled a previous preliminary ruling by an Advocate General in the government's favour.
The ECJ generally follows the opinion of an Advocate General in around 80% of cases.
Comments have been requested from the Department of Justice and Equality and An Garda Síochána.
The Department of Business Enterprise and Innovation, which oversees the WRC, said this is a matter that must go back to the Supreme Court, which had raised the question with the ECJ for consideration.
Neither the department nor the WRC will be commenting.
The ruling was welcomed by the Irish Human Rights and Equality Commission which provided legal representation for over a decade to two of the three Garda candidates challenging the discrimination rules.
It said that without today's ECJ ruling, people seeking to argue for national law conflicting with EU law to be disapplied would have had to start their cases in the High Court rather than the WRC - which would present what it called significant difficulties in terms of equity and access to justice for all.
IHREC Chief Commissioner Emily Logan said the case has wide impact and potential for positive change in the equality sphere.
Update 5 December: Statement from the Department of Justice and Equality & IHREC
"Yesterday morning the CJEU delivered its judgment which says that EU law takes precedence over national legislation and so any national body established by law (such as the WRC) must be given the power/jurisdiction to decide to disapply a rule of national law that is contrary to EU law.
"A number of practical matters obviously arise both specifically with this case and more generally and the department is considering the implications of the judgment."
Irish Human Rights and Equality Commission statement re ECJ ruling: (they funded the case for the 3 Garda candidates): Please add to online copy