Peter Sweetman and Others v An Bord Pleanála (Case C-258/11) EU:C:2013:220
Sweetman site integrity is one of the central Court of Justice judgments on Article 6(3) of the Habitats Directive and the meaning of an adverse effect on the integrity of a protected site.
The court held that permission can be given only where the competent authority is certain the project will not adversely affect site integrity. That is the case where no reasonable scientific doubt remains. Permanent and irreparable loss of habitat which forms part of the site’s essential characteristics can prevent that conclusion.
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- Neutral citation
- Case C-258/11, EU:C:2013:220
- Court
- Court of Justice of the European Union, Third Chamber
- Judgment date
- 11th April 2013
- Judge
- R. Silva de Lapuerta, K. Lenaerts, G. Arestis, J. Malenovský and T. von Danwitz
- Case number
- C-258/11
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What Sweetman site integrity decided
The reference arose from the proposed N6 Galway City Outer Bypass in Ireland. Part of the route would pass through the Lough Corrib protected site and permanently destroy an area of limestone pavement, a priority natural habitat.
An Bord Pleanála had concluded that the road would have a localised severe impact but would not adversely affect the integrity of the site overall. The Irish Supreme Court referred questions on the correct Article 6(3) test to the Court of Justice.
Site integrity is tied to the site’s conservation objectives
The court explained that the integrity of a site is linked to the lasting preservation of the characteristics which caused it to be designated.
A project can therefore adversely affect integrity where it is liable to prevent the lasting preservation of the constitutive characteristics connected with the presence of a priority habitat whose conservation justified designation of the site.
No reasonable scientific doubt must remain
Article 6(3) applies the precautionary principle. The competent authority may approve a project only after being certain that it will not adversely affect the protected site’s integrity.
Sweetman expressed that legal standard as the absence of any reasonable scientific doubt about the absence of adverse effects. Later cases, including Wyatt, explain how that rigorous standard operates in practical scientific assessment.
Permanent loss of priority habitat can be decisive
The court did not create a rule that every tiny loss of every habitat automatically means adverse effect on integrity.
Its reasoning focused on lasting harm to the ecological characteristics which justified the site’s designation. Where a project risks the disappearance or partial and irreparable destruction of a priority habitat forming part of those essential characteristics, the authority cannot lawfully conclude that integrity will remain unaffected.
Article 6(3) and Article 6(4) perform different jobs
The appropriate-assessment stage under Article 6(3) asks whether adverse effects on integrity can be ruled out to the required scientific standard.
If they cannot, that does not mean the Directive contains no possible route forward. Article 6(4) provides a separate derogation framework involving alternatives, imperative reasons of overriding public interest and compensatory measures. Those are not reasons for weakening the Article 6(3) integrity test.
Sweetman remains part of the current HRA framework
The case arose under EU law before the United Kingdom left the European Union, but the Article 6(3) principles continue to be highly important in the domestic Habitats Regulations framework and subsequent retained and assimilated case law.
For practical current guidance, see Planning Geek’s Habitats Regulations Assessment guide. It should be read with People Over Wind on mitigation at screening and Holohan on the scope of an appropriate assessment.
Read the full Sweetman judgment
The full Court of Justice judgment is held in the Planning Geek case law library. Gold Members can open the protected PDF below.
Sweetman Site Integrity Case Law Page Updated: 10th September 2026