Missing Conservation Objectives Do Not Automatically Require Quashing: Harmless Error and Declaratory Relief

1. Introduction

This judgment concerns the distinction between establishing an unlawful environmental assessment and obtaining an order quashing the resulting planning permission. An Coimisiún Pleanála had assessed a proposed wind farm without previously adopted site-specific conservation objectives for the Gearagh Special Protection Area. Following intervening clarification from the Court of Justice of the European Union, the parties accepted that this contravened the Habitats Directive.

The High Court nevertheless refused to quash the permission. The developer’s uncontested expert evidence established that the absence of those objectives had made no material difference to the assessment’s outcome. The court instead granted a declaration identifying the commission’s breach, supplementing an earlier declaration concerning the State’s failure to establish the objectives.

The decision principally applies, rather than invents, the doctrine of harmless error. Its particular significance lies in applying that doctrine after a CJEU ruling identifying conservation objectives as an essential precondition to a lawful appropriate assessment. It also develops a more restrictive, public-benefit-focused approach to declaratory relief where an established error does not justify quashing.

2. Background and the Remaining Dispute

The development and the parties

Gortyrahilly Wind DAC sought permission for a wind farm and associated infrastructure in Counties Cork and Kerry. The permitted scheme comprised 13 turbines, a 110 kV electrical substation and ancillary works. The application proceeded directly to the commission under the strategic infrastructure provisions of the Planning and Development Act 2000.

Wild Ireland Defence CLG, an environmental organisation which had participated in the planning process, challenged the permission. The commission, the relevant State respondents and the developer opposed the proceedings.

The application included an environmental impact assessment report, appropriate assessment screening documentation and a Natura impact statement. The commission’s inspectors and specialist advisers examined the project, and permission was granted on 25 February 2025, subject to conditions. The commission concluded that the development would not adversely affect the integrity of the relevant European sites.

The significance of the conservation objectives

Two Special Protection Areas featured prominently in the proceedings:

• Mullaghanish to Musheramore Mountains SPA: site-specific conservation objectives had been published in September 2022, before the planning decision.
• Gearagh SPA: site-specific conservation objectives were not published until 25 April 2025, two months after permission was granted.

The surviving issue concerned the Gearagh SPA’s qualifying interests: Wigeon, Teal, Mallard, Coot, and “Wetland and Waterbirds”. The question was whether conducting an appropriate assessment without the necessary objectives required the permission to be quashed.

What had already been decided

In Wild Ireland Defence CLG v An Coimisiún Pleanála and Others (No. 1) [2025] IEHC 726, the court had disposed of the other grounds. These included challenges concerning the other SPA, non-qualifying bird species, conservation measures and language-related issues. By consent, it granted a declaration that the relevant State respondents had failed to establish site-specific conservation objectives for the Gearagh SPA as required by EU law.

Only the outstanding part of Core Ground 3 remained. It had been reserved pending the CJEU’s judgment in the joined Knocknamona/Massey proceedings. The second module was therefore not a reopening of the entire environmental challenge.

The decisive evidence

After the first judgment, the principal author of the original Natura impact statement produced an updated statement addressing the subsequently published objectives. The expert concluded that, with the relevant mitigation measures implemented, the development would have no effects on those objectives.

The applicant’s responding expert affidavit addressed the Mullaghanish to Musheramore Mountains SPA, rather than answering the updated assessment concerning the Gearagh SPA. Since the former challenge had already been dismissed, that affidavit did not provide a relevant evidential contest on the issue remaining for determination.

3. Summary of the Decision

The court’s conclusions were:

1. The commission had committed a legal error. It could not lawfully conduct the relevant appropriate assessment without previously adopted site-specific conservation objectives.
2. Quashing did not follow automatically. The developer established that the error was harmless, excluding a reasonable possibility that it affected the actual outcome.
3. A declaration was nevertheless appropriate. The court separately marked the commission’s decision-making breach, which differed from the State-level failure already declared.
4. No further CJEU reference was necessary. The court considered the applicable principles of harmless error sufficiently settled.
5. Costs were provisionally divided by outcome. The applicant was to receive limited costs attributable to the successful declarations, with otherwise no order as to costs, subject to further submissions.

The permission consequently remained in place. This was not a finding that the original appropriate assessment had become lawful retrospectively. It was a decision that the established unlawfulness did not warrant the particular remedy of certiorari.

4. The Statutory and EU Law Framework

Article 6(3) of Directive 92/43/EEC—the Habitats Directive—requires an appropriate assessment where a plan or project is likely to have a significant effect on a protected site. The competent authority must assess the implications for the site in light of its conservation objectives and satisfy itself that the proposal will not adversely affect the site’s integrity.

Article 7 applies the relevant Habitats Directive protections to Special Protection Areas classified under the Birds Directive, now Directive 2009/147/EC. In Irish planning law, sections 177U and 177V of the Planning and Development Act 2000 govern screening and appropriate assessment.

The judgment separates three legally distinct matters:

• The State’s obligation: establish the required conservation objectives.
• The commission’s obligation: conduct a lawful assessment using those objectives.
• The reviewing court’s function: determine the appropriate remedy for an established breach.

Failure at the first or second stage establishes unlawfulness. It does not, on the court’s analysis, necessarily predetermine the third.

5. The Principal Authorities and Their Influence

5.1 The substantive requirement: conservation objectives must come first

The immediate legal foundation was the CJEU’s decision in Joined Cases C-27/25 (Knocknamona) and C-356/25 (Massey). As reproduced in this judgment, the CJEU held that a national authority cannot conduct a valid appropriate assessment where conservation objectives specific to the SPA have not previously been adopted.

The objectives are not optional information to be considered only if available. Determining them is an essential preliminary stage in the Article 6(3) process. The CJEU also distinguished identifying the geographical area potentially affected from evaluating the likelihood of significant effects on a protected site within that area: the latter evaluation requires the site’s conservation objectives.

This authority resolved the legality question against the commission. However, Humphreys J. held that it did not resolve the separate question of remedial discretion. The references had not asked the CJEU to determine the application of harmless error.

5.2 The central remedial authority: Altrip

Gemeinde Altrip and Others v Land Rheinland-Pfalz, C-72/12, ECLI:EU:C:2013:712, supplied the principal EU foundation for the court’s approach. Although that case concerned the Environmental Impact Assessment Directive, the judgment treated its remedial reasoning as applicable to the present environmental assessment defect.

Three features were especially important:

• A defect does not necessarily justify setting aside a development decision if it could not have affected the decision’s substance.
• The reviewing court may use evidence supplied by the developer or competent authorities when deciding whether the defect mattered.
• The burden of demonstrating harmlessness must not be transferred to the applicant.

Altrip therefore answered the applicant’s objection that receiving an updated Natura impact statement would improperly turn the court into the assessment authority. The court considered that it was evaluating the consequences of an error for remedial purposes, not undertaking the commission’s statutory assessment afresh.

The judgment also recognised that material interference with public participation matters. Harmlessness cannot be reduced to asking whether the final permission appears environmentally acceptable while ignoring a lost procedural right capable of affecting the decision.

5.3 Supreme Court guidance on invalidity and discretion

In Pat O'Donnell & Co. v. Dublin City Council [2026] IESC 36, the Supreme Court distinguished between a legislative requirement whose breach was intended to produce invalidity and a breach whose consequences fall to be assessed through principled discretion.

Humphreys J. drew from that decision a two-stage inquiry:

1. Does the applicable legal rule require invalidity as the consequence of non-compliance?
2. If not, do the circumstances justify withholding relief, considering substantial compliance, prejudice, the seriousness of the breach and relevant public interests?

The Supreme Court’s description of harmless error as potentially “old wine in new bottles” was important. It located the doctrine within established questions about prejudice and discretionary relief rather than treating it as an exceptional new defence.

Amariei v. Chief Appeals Officer [2026] IESC 22, Kelly v. Minister for Agriculture [2021] IESC 62 and Christian v. Dublin City Council [2012] IEHC 163 supplied a corresponding limitation: discretion is not freedom to decide according to judicial preference. Withholding an otherwise justified order must rest on a sufficiently weighty constitutional or legal value.

The decisions in Protect East Meath v. Meath County Council [2026] IESC 1 and [2026] IESC 12 reinforced the complementary requirements that statutory obligations be respected and remedies have practical utility. The judgment thus presented discretion as a legally bounded exercise, not a licence to disregard mandatory environmental requirements.

5.4 The domestic harmless-error cases

Carrownagowan Concern Group v. An Bord Pleanála (No. 3) [2024] IEHC 549 supported considering the whole administrative record together with further admissible evidence when assessing materiality. It also supported distinguishing judicial evaluation of harmlessness from substitution of the court’s environmental judgment for that of the planning authority.

The subsequent determination in Carrownagowan Concern Group v. An Bord Pleanála [2025] IESCDET 9 regarded the general proposition that not every error requires quashing as well established. It also recognised that Altrip permits reliance on developer evidence.

Massey v. An Bord Pleanála (No. 2) [2025] IEHC 206 was particularly close factually. There, the court concluded that missing conservation objectives could not affect the screening outcome on the evidence. It dismissed the claim for certiorari while leaving a reference capable of supporting declaratory relief. The procedural history demonstrated that the legality question and the quashing question could be separated.

In Massey v. An Bord Pleanála [2025] IESCDET 126, the Supreme Court refused leave to appeal and referred to the uncontested evidence that the objectives’ absence made no difference. Humphreys J. relied on this treatment while expressly acknowledging the non-precedential character of leave determinations.

Doyle v. An Bord Pleanála [2025] IEHC 158 and Ryanair Designated Activity Company v. An Bord Pleanála [2025] IEHC 194 further supported the proposition that the doctrine is not confined to minor clerical or narrowly technical defects. Describing an assessment requirement as “jurisdictional” does not itself eliminate remedial discretion.

Related authorities, including Reilly v. An Coimisiún Pleanála [2025] IEHC 659 and Ballyboden Tidy Towns Group v. An Bord Pleanála [2023] IEHC 722, supported the rejection of automatic nullity. The Supreme Court decision in Ballyboden Tidy Towns Group v. An Bord Pleanála [2024] IESC 4 also supported the court’s ability to consider discretion and the developer’s ability to defend a permission independently of the decision-maker.

5.5 Evidence and scientific certainty

RAS Medical Ltd v. Royal College of Surgeons in Ireland [2019] IESC 4 was central to the treatment of affidavit evidence. Material factual conflicts generally cannot simply be resolved against the party who does not carry the burden where no cross-examination has occurred.

That principle cuts both ways. Applicants ordinarily bear the burden of establishing an assessment defect, as recognised in An Taisce v. An Bord Pleanála & Ors. [2022] IESC 8. Once error is established, however, the party asserting harmlessness carries the relevant burden. Properly controverted developer evidence may therefore fail to establish harmlessness unless the conflict is resolved.

The judgment also drew on Landelijke Vereniging tot Behoud van de Waddenzee and Nederlandse Vereniging tot Bescherming van Vogels v Staatssecretaris van Landbouw, Natuurbeheer en Visserij, C-127/02, and Holohan v An Bord Pleanála, C-461/17. These authorities informed its distinction between reasonable scientific doubt and impossible demands for absolute certainty. The harmless-error inquiry likewise concerns reasonable possibilities, not every theoretical scenario.

5.6 Supporting UK authorities

Walton v. Scottish Ministers [2012] UKSC 44 and R (Champion) v. North Norfolk District Council [2015] UKSC 52 supplied comparative support for a practical, non-automatic approach to environmental remedies.

Canterbury City Council v. Secretary of State for Housing Communities and Local Government [2019] EWHC 1211 (Admin.) supported judicial consideration of whether a defect affected the result. In R (Bradbury) v Brecon Beacons National Park Authority [2025] EWCA Civ 489, the court similarly considered whether a planning committee’s decision would have been substantially different had the missing assessment information been before it.

These decisions were supporting authorities rather than substitutes for the applicable Irish and EU principles.

5.7 The limit: material EU law breaches

The judgment expressly distinguished harmless error from a breach which materially affects the outcome. Relying on Commission v Ireland (Derrybrien Wind Farm), C-261/18, ECLI:EU:C:2019:955, it stated that material EU law breaches should normally be remedied by certiorari, with after-the-event assessment permitting a permission to stand confined to exceptional circumstances.

This qualification is fundamental. The judgment does not establish that any defective assessment can be repaired through litigation evidence. Its reasoning depends on evidence that the particular defect made no material difference.

6. How the Court Applied Those Principles

6.1 The burden shifted once error was established

The parties agreed both that the commission had erred and that the opposing parties carried the burden of showing why certiorari should not follow. The judgment therefore did not require the applicant to prove ecological damage as a precondition to obtaining a remedy.

The developer met its burden through the updated Natura impact statement and supporting affidavit. Those materials addressed the newly available objectives and concluded that they did not alter the relevant assessment conclusions. The court accepted that evidence.

The applicant offered no expert answer concerning the Gearagh SPA. Its evidence instead revisited an already dismissed challenge concerning another site. The decisive evidential position was consequently not merely that the applicant had failed to establish harm, but that the developer had positively established immateriality without a relevant evidential contest.

6.2 The test was reasonable possibility, not absolute certainty

At paragraph 85, the court’s working formulation was that it should:

“exclude a reasonable possibility that the error would have made a difference to the actual outcome”.

A change in the wording of the assessment would not necessarily constitute a material change in outcome. Conversely, evidence suggesting a reasonably possible different substantive result would prevent the court from treating the error as harmless.

This distinction avoids two extremes: automatic quashing for every defect, and preservation of a permission merely because a court considers the same outcome probable.

6.3 “Jurisdictional” did not mean automatic certiorari

The applicant argued that conservation objectives were a jurisdictional prerequisite and that their absence necessarily required quashing. The court rejected that inference.

A mandatory precondition determines what the commission may lawfully do. It does not necessarily prescribe what order a reviewing court must make after a breach. The judgment relied in this respect on Coolglass Wind Farm Ltd v. An Coimisiún Pleanála [2026] IESC 5, where the Supreme Court separately considered vires and the discretionary consequences of the identified error.

The important distinction is between the authority’s legal power to decide and the court’s remedial jurisdiction. Calling an error “jurisdictional” cannot collapse those questions into one.

6.4 The applicant’s participation remained relevant

The applicant had not advanced the conservation-objectives prerequisite in its own planning submission. The court held that this did not bar the challenge, but was relevant to discretion. Related submissions from other participants did not entirely remove that consideration.

This was not a ruling that environmental organisations must exhaust every legal argument administratively before approaching the court. Nor did it remove the commission’s autonomous obligations. It treated the applicant’s conduct as one factor in selecting a remedy after unlawfulness had been established.

6.5 Finality prevented reopening dismissed issues

The applicant’s supplemental affidavit could not revive the challenge concerning the Mullaghanish to Musheramore Mountains SPA. Preparing evidence for a possible appeal did not make that evidence admissible in the remaining trial module.

The court considered the affidavit inadmissible or without weight. This illustrates a practical consequence of modular litigation: once a module finally disposes of an issue, a later module is not an opportunity to improve the evidence on that issue.

The insistence on defined issues was consistent with the pleading principles discussed in Concerned Residents of Treascon and Clondoolusk v. An Bord Pleanála [2024] IESC 28, including the need for particular clarity in complex EU law challenges.

7. Climate Obligations, Proportionality and Their Limits

Alongside evidential harmlessness, the court identified several discretionary considerations supporting refusal of certiorari:

• the legally supported urgency of renewable energy infrastructure;
• the disproportionate impact of quashing on the developer;
• the project’s lengthy progress since the September 2022 application;
• the applicant’s failure to raise the particular point during the planning process; and
• the availability of a declaration as a more proportionate response.

The climate context was grounded in law, including the Climate Action and Low Carbon Development Act 2015 as amended, the European Climate Law and Directive (EU) 2023/2413, commonly called RED III. The court also referred to Verein KlimaSeniorinnen Schweiz and Others v Switzerland and international advisory opinions concerning climate obligations.

These materials supported the weight attached to avoiding unnecessary delay in renewable energy delivery. They did not establish that climate benefits erase Habitats Directive requirements.

Indeed, the court expressly left unresolved a possible further EU law question concerning whether renewable energy’s overriding public importance could affect remedies for a breach that did have counterfactual consequences. Its reference to the pending Eneco Wind Belgium, C-325/25, was obiter. Because harmlessness had been established here, that wider question did not require decision.

The judgment should therefore not be read as authorising a general balancing away of adverse effects on protected sites, or as conducting an Article 6(4) derogation exercise.

8. Declaratory Relief: A Separate and More Nuanced Inquiry

The governing authorities

In B. v. Child & Family Agency & Ors. [2025] IESC 2, the Supreme Court identified three central features supporting declaratory relief: a good reason for seeking it, a real and substantial issue, and a party with a real interest in opposing it.

Drawing also on Save The South Leinster Way v. An Coimisiún Pleanála (No. 2) [2025] IEHC 541, Humphreys J. set out a more detailed practical framework. Although not inflexible conditions, the relevant considerations were:

1. An established legal error.
2. Refusal of certiorari or other imperative relief, so that the declaration serves an independent purpose.
3. A declaration directed to the specific error, rather than an unnecessary general statement of law.
4. Normally, prior denial of the error by the decision-maker.
5. A sufficiently affirmative public benefit or comparably strong reason for formally marking the breach.
6. No overriding discretionary reason to refuse declaratory relief itself.

The significance of prior denial

The fourth consideration is a notable refinement. The court was concerned that treating every admission of error as automatically requiring a declaration and costs would encourage unnecessary litigation and discourage early concessions.

It therefore envisaged room for a respondent to acknowledge error while maintaining that the error was harmless, without inevitably facing declaratory relief. This was expressed as an ordinary consideration, not an absolute immunity arising from admission.

Here, the commission had denied the error until the intervening CJEU judgment. Its later acceptance did not prevent the court from finding this consideration satisfied.

Why a declaration was granted here

The existing declaration concerned the State’s failure to establish objectives. The further declaration concerned a different legal wrong: the commission’s conduct of an appropriate assessment without them.

The court considered that the unusual circumstances and public benefit justified recording that distinct breach. The operative declaration identified the commission’s contravention of Article 6(3), applied to SPAs through Article 7, in conducting the assessment underlying its decision of 25 February 2025.

The wording “in circumstances where” the State had failed to comply was deliberate. It connected the two failures without treating the commission’s conduct as an inevitable consequence for which it had no independent agency.

The resulting approach preserves accountability without treating a declaration as an automatic consolation remedy whenever certiorari is refused.

9. Why No Further CJEU Reference Was Made

The applicant proposed a reference asking whether relief could be withheld where there was no valid appropriate assessment.

The court declined. Under Article 267 TFEU, a reference must concern an interpretation or validity question necessary to determine the proceedings. The principles in Srl CILFIT and Lanificio di Gavardo SpA v Ministry of Health, Case 283/81, and Consorzio Italian Management and Catania Multiservizi SpA v Rete Ferroviaria Italiana SpA, C-561/19, also recognise that a reference is unnecessary where the answer is sufficiently clear or already established.

Humphreys J. considered Altrip to have settled the relevant remedial principle. The later Knocknamona/Massey ruling addressed the assessment’s legality, not harmless error, and had not displaced that principle.

The court also relied on the distinction between interpreting EU law and applying established law to proven facts. Authorities including Eco Advocacy v. An Bord Pleanála [2025] IESCDET 74 supported refusing references on questions which do not properly arise in the proceedings.

Analytically, the strongest foundation for the refusal was the court’s reliance on existing authority and its separation of legality from remedy. The CJEU’s silence about harmless error in a reference not asking that question cannot itself be treated as an affirmative ruling approving every aspect of the domestic approach.

10. Costs and Responsible Environmental Litigation

The court provisionally allowed costs attributable to the declarations, limited to what would have been incurred had the applicant confined the proceedings to the relief obtained. This was not an award of the costs of the unsuccessful challenge to the permission.

For the remainder, the provisional position was no order as to costs. The operative order allowed contrary submissions within seven days, so these costs arrangements should not be described as unconditional final determinations.

The section 50B exception

The judgment examined when section 50B(3) of the Planning and Development Act 2000 permits adverse costs despite environmental costs protection. Drawing on Dunne v. Guessford Limited [2022] IEHC 427, it distinguished a reasonable but unsuccessful submission from unreasonable litigation conduct.

Potentially relevant conduct included:

• advancing evidence-dependent allegations without evidence;
• introducing inadmissible or irrelevant material;
• rearguing settled points without a substantial basis for reconsideration;
• unnecessarily consuming hearing time; and
• failing to comply with procedural obligations.

Permanent TSB & ors v. Skoczylas & ors [2021] IESC 10 supported using costs to encourage efficient litigation. Hunter v. Environmental Protection Agency [2013] IEHC 591 established that moral wrongdoing is not necessary before the statutory exception can apply. Sweetman v. Shell E&P Ireland Limited and ors. [2016] IESC 58 informed the emphasis on focused, evidentially grounded environmental proceedings.

Despite concerns about aspects of this litigation, the court did not propose an adverse costs order. It gave weight to the applicant’s narrowing of its case and the limited hearing time used. That qualification matters: the judgment warned against unreasonable conduct without finding that the litigation, viewed overall, warranted a costs penalty.

11. Wider Impact and Critical Assessment

A fact-sensitive route to preserving permissions

The judgment strengthens the practical distinction between a defective assessment and a permission which must be quashed. Developers and authorities facing an established assessment defect may seek to prove its immateriality through focused expert evidence.

However, the result depends on the quality and scope of that evidence. An updated report which merely asserts safety, relies on new mitigation essential to the outcome, or fails to answer the particular defect may present a materially different case. The judgment does not make late evidence self-validating.

The importance of answering the correct issue

For challengers, the immediate lesson is evidential. Once harmlessness is supported by relevant expert material, objections directed only to the legal availability of the doctrine may be insufficient. Any factual contest must address the site, conservation objectives and alleged consequences actually remaining in issue.

That does not reverse the burden of proof. It recognises that a party carrying that burden may discharge it through credible, unanswered evidence.

The boundary between remedy and reassessment

The distinction between considering harmlessness and performing an assessment is persuasive where the inquiry is narrow and the evidence uncontested. It becomes more difficult where the court must choose between competing ecological methodologies or where later objectives introduce materially different conservation requirements.

The judgment’s reliance on the burden of proof, cross-examination principles and the reasonable-possibility threshold provides safeguards against allowing remedial proceedings to become an unrestricted substitute planning process.

A restrained approach to declarations

The declaration framework may discourage claims brought solely to obtain a formal acknowledgment of an admitted, harmless breach. At the same time, this case shows that absence of demonstrated environmental consequences does not eliminate the public value of identifying institutional non-compliance.

The distinction between State responsibility and decision-maker responsibility is especially useful. It prevents one declaration from obscuring a separate breach by another public body.

The judgment’s precedential reach

This is a High Court application of established principles, not a new CJEU ruling on the precise relationship between Altrip and every Article 6(3) defect. Its strongest factual feature was the uncontested evidence concerning the only remaining SPA. Cases involving disputed ecological consequences, impaired participation or a material difference in outcome remain distinguishable.

12. Complex Concepts Simplified

Special Protection Area

A site protected under EU birds legislation because of its importance for particular birds and their habitats.

Site-specific conservation objectives

The conservation goals for a particular protected site. They provide the benchmark against which a project’s effects must be assessed.

Appropriate assessment

A detailed examination of whether a proposal could adversely affect a protected site’s integrity, measured against its conservation objectives.

Natura impact statement

The developer’s scientific information supporting that assessment. It informs, but does not replace, the authority’s own statutory assessment.

Certiorari

A court order quashing an administrative decision. Here, it would have set aside the planning permission.

Harmless error

An established legal mistake shown not to have materially affected the outcome. The mistake remains unlawful, but quashing may be unnecessary.

Declaratory relief

A formal statement of the legal position. It can identify a public authority’s breach without setting aside its decision.

Acte clair and acte éclairé

Situations where an EU law answer is sufficiently clear, or already established, so that a further CJEU reference is unnecessary.

13. Conclusion

The judgment confirms that mandatory environmental obligations and proportionate judicial remedies are separate questions. The commission acted unlawfully by assessing the Gearagh SPA without the required conservation objectives. Nevertheless, the developer proved that the omission made no material difference, and the permission was not quashed.

Its broader message is carefully bounded: harmlessness must be proved by the party asserting it; material EU law breaches normally require effective corrective relief; and declarations remain available where formally identifying a distinct breach serves a sufficient public purpose.