Public-Interest Costs After an Unsuccessful Mootness Appeal: Limited Reach of Little and Partial Costs Against “Pathfinder” Litigants

1. Introduction

This Supreme Court ruling concerns costs only in two linked judicial review proceedings: KE v The International Protection Appeals Tribunal & ors and FOM v. The Minister for Justice & Ors ([2026] IESC 17). The underlying litigation challenged State decision-making connected with returning international protection applicants to the United Kingdom as a designated “safe third country”.

In the High Court, the applicants succeeded and obtained certiorari and declarations, including a declaration that the UK’s designation as a safe third country was contrary to EU law. The State appealed. After legislative change and revocation of the relevant designation instrument, the Court of Appeal treated the State’s appeal as moot. The Supreme Court subsequently reversed that mootness finding (see [2026] IESC 8). The only remaining issue in this decision is: who should bear the costs of the mootness litigation in the Court of Appeal and Supreme Court?

The applicants argued that, because these were “pathfinder” test cases raising significant EU/constitutional issues, they should receive costs protection (or at least not have costs awarded against them), relying on the principles in Little v Chief Appeals Officer [2024] IESC 53.

2. Summary of the Judgment

The Supreme Court held that, although the underlying asylum/EU law questions were important, the appellate proceedings to date had addressed only mootness, decided on case-specific facts and without any development of legal principle. Accordingly, the appeal did not fall within the categories identified in Little v Chief Appeals Officer [2024] IESC 53 that might justify shielding an unsuccessful public-interest litigant from an adverse costs order.

The Court therefore ordered:

  • Full costs to the State parties in the Court of Appeal (in respect of the mootness hearing and related costs application).
  • 50% of the State parties’ costs in the Supreme Court.

The Court noted that High Court costs remained to be determined in the substantive appeal (which had not yet been decided on the merits).

3. Analysis

3.1 Precedents Cited

(a) Little v Chief Appeals Officer [2024] IESC 53

Role in this ruling: Little was the applicants’ principal authority for resisting an adverse costs order, or for seeking partial costs in their favour despite losing on mootness.

The Supreme Court summarised (via the parties’ submissions) the Little approach: costs protection for an unsuccessful public interest litigant should be confined to cases of “real substance” with “clear, significant public interest”, typically featuring:

  • “foundational” constitutional or EU issues,
  • conspicuous novelty,
  • far-reaching general importance,
  • clarification of obscure/unexplored areas, or
  • a claimant who loses overall but wins a significant issue.

How it influenced the outcome: The Court treated Little as setting the relevant framework—but held that framework was not engaged here because the appellate litigation did not, in fact, determine (or even debate) the foundational EU/constitutional questions; it determined only mootness.

(b) [2026] IESC 8

Role in this ruling: This was the earlier Supreme Court decision in the same overall dispute, where the Court held the State’s appeals were not moot. In [2026] IESC 17, that determination is the backdrop to costs: the State had “been entirely successful” on mootness and sought costs accordingly.

How it influenced the outcome: Because the State succeeded on the only issue argued in the Supreme Court (mootness), the ordinary costs consequence (“costs follow the event”) strongly favoured a costs order for the State, subject only to any Little-type public interest moderation.

(c) [2025] IECA 43

Role in this ruling: The Court of Appeal decision that found the appeals moot and awarded costs to the applicants for the mootness hearing. The Supreme Court’s reversal of mootness (in [2026] IESC 8) necessitated revisiting the costs consequences of that Court of Appeal hearing.

How it influenced the outcome: Once the mootness finding was reversed, the earlier costs outcome in the Court of Appeal no longer reflected the “event” on which costs typically follow. This supported awarding the State its Court of Appeal costs.

(d) [2024] IEHC 183

Role in this ruling: This was referenced only as the High Court judgment from which leave to appeal and cross-appeal was granted on extensive EU law and statutory issues (safe third country safeguards, methodology, rights scrutiny at return, non-transposition, non-regression, and data transfer).

How it influenced the outcome: It contextualised the applicants’ argument that the litigation was of major public importance. However, the Supreme Court drew a sharp line between (i) the importance of the underlying merits and (ii) what was actually litigated on appeal to date (mootness only).

3.2 Legal Reasoning

  1. Identify what the appellate courts actually decided: The Court emphasised that the significant EU/constitutional issues highlighted by the applicants were not determined by either the Court of Appeal or the Supreme Court, because the Court of Appeal stopped at mootness and the Supreme Court addressed only whether the appeal was moot.
  2. Characterise the mootness issue as non-developmental and fact-specific: The Court noted there was no dispute about the applicable principles governing mootness; it was not asked to revisit authorities or develop the doctrine. The mootness decision turned on case-specific features.
  3. Apply the Little threshold to the proceedings as run, not to the proceedings as originally framed: Although the underlying issues were “of significant importance”, the costs question had to be assessed by reference to the issue actually contested on appeal. On that basis, the appeal could not be said to fit the Little categories.
  4. Address “pathfinder” status without granting blanket immunity: The Court accepted these were “pathfinder” cases, but held that the absence of costs exposure for other applicants in the cohort could not “entirely dissipate” the consequences of these respondents’ choice to litigate mootness.
  5. Fashion a proportionate costs order: The Court awarded the State full Court of Appeal costs and only 50% of Supreme Court costs, reflecting a calibrated approach: the State succeeded, but the litigation context and public-interest dimension justified some moderation at Supreme Court level.

3.3 Impact

  • Public-interest/test litigation does not automatically confer costs protection: Even in “pathfinder” litigation involving significant EU/asylum policy questions, a party may face adverse costs if they pursue (and lose) an interlocutory/appellate issue that does not advance or clarify the law.
  • Focus on the issue actually litigated: The decision signals that Little-type cost moderation will be assessed by reference to the substance of what the appellate court was required to decide, not merely by the headline importance of the underlying proceedings.
  • Mootness appeals may carry ordinary costs risk: Where mootness is argued as a case-management/off-ramp and does not entail doctrinal development, the Supreme Court indicates a reluctance to treat such litigation as falling within the “foundational/novel” public-interest costs category.
  • Partial costs as a middle course: The 50% Supreme Court costs order illustrates a practical tool for courts to reflect context and fairness without displacing the general rule that costs follow the event.

4. Complex Concepts Simplified

  • Certiorari: a court order quashing (setting aside) an administrative decision because it was unlawful.
  • Declaratory relief: a binding statement by the court on what the law is or whether a legal position/action is lawful, without necessarily granting further orders.
  • Safe third country: a state deemed sufficiently safe such that an asylum seeker may be transferred/returned there to seek protection, subject to legal safeguards.
  • Non-refoulement: the principle that a person must not be returned to a place where they face a real risk of persecution, serious harm, or other prohibited ill-treatment.
  • Mootness: an issue is moot where, because of intervening events (such as legislative change), a court’s decision would no longer have practical effect between the parties.
  • Pathfinder case: a test case selected to decide issues that arise in many similar cases, providing guidance for the remainder.
  • “Costs follow the event”: the usual rule that the losing party pays the winning party’s legal costs, subject to the court’s discretion.

5. Conclusion

[2026] IESC 17 establishes a clear costs message: public-interest significance in the underlying proceedings is not enough to attract Little-style protection where the appeal actually litigated is a fact-specific mootness dispute that does not develop legal principle. Even in “pathfinder” litigation, parties who choose to fight (and lose) mootness may face adverse costs—though the Court may still moderate the order, as shown by the award of 50% of Supreme Court costs rather than full costs.