Short answer
An Irish superior court may declare legislation invalid where it is repugnant to the Constitution. The High Court has original jurisdiction, with appeals through the Court of Appeal and ultimately the Supreme Court. The claimant needs a justiciable dispute and standing and must identify the constitutional rule infringed. Relief may be limited by severability and finality.
Executive and administrative action is reviewed more broadly. A court may quash a decision that is outside statutory or constitutional power, procedurally unfair, based on an error of law, irrational, disproportionate where rights are engaged, or otherwise unlawful. The court controls legality, not the merits of policy, and remedies remain discretionary.
EU law and the European Convention on Human Rights Act 2003 produce different results. Within EU law's scope, a national court must disapply a conflicting national rule so that directly effective EU law prevails. Under the ECHR Act, courts interpret legislation compatibly so far as possible, can remedy an unlawful act by an organ of the State, and may declare legislation incompatible—but that declaration does not invalidate the legislation.
Constitutional invalidity of legislation
Article 15.4 states the substantive rule:
“The Oireachtas shall not enact any law which is in any respect repugnant to this Constitution”
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Under Article 34.3.2, the High Court has full original jurisdiction to determine the validity of a law having regard to the Constitution; no lower court may decide that question. Appeals follow the constitutional court hierarchy. If a provision is invalid, it is invalid to the extent of the repugnancy. A court will consider whether the offending part can be severed without rewriting the legislative scheme.
The challenge must concern a real legal dispute. Ordinarily, a claimant must show that the impugned provision affects their rights or interests and should not litigate another person's hypothetical rights. Irish standing rules can accommodate genuine public-interest litigation where the constitutional issue would otherwise evade review, as the plaintiff's standing in illustrates.
Legislation benefits from a presumption of constitutionality, including an assumption that it will be administered constitutionally where the text permits. That cannot justify a saving construction inconsistent with the enacted language. Rights restrictions are commonly tested for a legitimate objective, rational connection, necessity and proportionate balance.
Two special limits matter. A Bill referred by the President under Article 26 and upheld by the Supreme Court generally receives immunity from later constitutional challenge under Article 34.3.3. Article 28.3.3 also protects specified emergency legislation from ordinary constitutional invalidity, subject to its terms. Neither exception should be assumed without checking the particular enactment and constitutional text.
Judicial review of executive and administrative action
Executive power must come from the Constitution or lawful legislation and be exercised within its limits. Judicial review can address lack or excess of jurisdiction, misconstruction of an enabling Act, unlawful delegation, irrelevant considerations, failure to consider mandatory matters, objective bias, denial of fair procedures, irrationality and breach of constitutional rights. Where a fundamental right is materially affected, proportionality may sharpen the intensity of review, as explained in .
The usual remedies include certiorari, prohibition, mandamus, declarations and injunctions. Damages require an independent legal basis. The claimant should seek leave promptly: Order 84 generally uses a three-month limit, while specialist legislation can be shorter. Delay, an adequate alternative remedy or lack of practical utility may affect relief.
Judicial review is not an appeal on the facts. A court may require lawful reasons, procedures and statutory compliance without choosing the government's preferred policy. In , the Supreme Court quashed the national mitigation plan for failing to satisfy its statutory requirements while preserving the institutional distinction between legal review and climate-policy design.
EU law usually requires disapplication, not domestic invalidity
Article 29.4 constitutionally accommodates Ireland's EU membership and protects laws enacted, acts done and measures adopted that are necessitated by EU obligations. That protection is not a blanket immunity for every measure merely associated with EU policy. Whether an act was necessitated and whether it exceeds constitutional authority can still require careful analysis.
Where a national provision conflicts with directly effective EU law, every competent Irish court must give full effect to EU law and disapply the conflicting national rule in the case before it. The national measure is not necessarily erased or invalid for all non-EU purposes. The court must identify EU scope, direct effect, the relevant implementing measure and any available conforming interpretation before stating the remedy.
Questions of EU interpretation or validity may be referred under Article 267 TFEU. A national court cannot itself declare an EU act invalid. A final-instance court must refer a necessary unresolved interpretation question unless a recognised exception applies. National procedure must respect equivalence, effectiveness and effective judicial protection.
EU membership does not remove all constitutional limits on international action. In Crotty, the Supreme Court held that the Government could not bind the State to the foreign-policy constraints at issue without constitutional authority. In , the Court held that Ireland could not ratify CETA under the law then in force, while a legislative amendment could remove the identified obstacle.
The ECHR Act does not strike down legislation
The Convention is given effect in domestic law through the European Convention on Human Rights Act 2003, not by making it a superior constitutional code. Section 2 requires compatible interpretation of statutory provisions and rules of law “in so far as is possible”, subject to ordinary interpretation rules. A court cannot use section 2 to contradict an unmistakable legislative choice.
Under section 3, every organ of the State must perform its functions compatibly with the State's Convention obligations, subject to any contrary statutory provision or rule of law. A person injured by a contravention may seek damages where no other damages remedy is available; a one-year limitation normally applies, extendable in the interests of justice.
If compatible interpretation and other adequate remedies are unavailable, the High Court, Court of Appeal or Supreme Court may make a declaration of incompatibility under section 5, as amended in 2014. Its effect is deliberately limited:
“shall not affect the validity, continuing operation or enforcement”
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The declaration informs the political branches and can support an ex gratia compensation application, but the rule remains law. demonstrates the mechanism in local-authority possession proceedings.
Separation of powers supplies both grounds and limits
Article 15.2 vests the sole and exclusive power of making laws for the State in the Oireachtas. The legislature may confer rule-making power, but must determine the governing principles and policies rather than transfer an essentially legislative choice without standards. Delegated legislation that exceeds its parent Act or constitutional limits can be quashed.
Articles 34 and 37 distinguish the administration of justice in courts from limited judicial functions that may be exercised elsewhere. In , the Supreme Court treated Workplace Relations Commission adjudication as the administration of justice, examined Article 37's limits and required constitutionally adequate safeguards including public hearings, evidence on oath and fair procedures.
Separation of powers also restrains courts. They interpret and enforce law, but do not draft a substitute legislative scheme, administer departments or decide political merits. Conversely, describing an issue as policy or international relations does not make unlawful executive action immune from review. Crotty, Friends of the Irish Environment and Costello each show courts policing the legal boundary while leaving permissible policy choices to elected institutions.
Effects, finality and practical steps
A declaration of constitutional invalidity can have profound consequences, but it does not automatically reopen every final judgment made under the former understanding of the law. emphasises finality, res judicata and legal certainty. The result depends on the proceedings, the remedy sought and whether the earlier decision remains final.
A claimant should identify the challenged act, legal power, standing, time limit and respondent. Separate constitutional, judicial-review, EU-law and ECHR Act grounds because each has a different remedy. Preserve the decision, reasons and record, and consider interim relief before irreversible action.
Conclusion
Irish courts can invalidate unconstitutional legislation and quash unlawful executive action, but EU and ECHR review must not be described as the same remedy. EU primacy ordinarily produces disapplication within EU scope; the ECHR Act favours compatible interpretation, State-organ remedies and a non-invalidating declaration. Across all four routes, separation of powers authorises courts to enforce legal limits while preventing them from assuming legislative or executive functions.
Sources
This article provides general legal information, not advice for a specific matter. Laws, facts and procedural deadlines may change the result. Follow the linked primary sources and obtain local advice before acting.