Brian Holohan and Others v An Bord Pleanála (Case C-461/17) EU:C:2018:883
Holohan appropriate assessment is an important Court of Justice judgment on how wide and how detailed a Habitats assessment must be before a project affecting a protected site can be authorised.
The assessment must identify and examine all aspects of the project which can affect the site’s conservation objectives. That can include effects on habitat types and species outside the formal site boundary where those effects could in turn affect the protected site’s integrity.
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- Neutral citation
- Case C-461/17, EU:C:2018:883
- Court
- Court of Justice of the European Union, Second Chamber
- Judgment date
- 7th November 2018
- Judge
- A. Prechal, C. Toader and A. Rosas
- Case number
- C-461/17
What Holohan appropriate assessment decided
The reference arose from a major road scheme in Ireland. The proposed route could affect several European protected sites and raised questions about what the appropriate assessment had to identify, examine and explain.
The Court of Justice confirmed that Article 6(3) requires a complete assessment capable of removing reasonable scientific doubt about adverse effects on site integrity.
All aspects which can affect conservation objectives must be identified
Before a project is approved, the competent authority must identify all aspects of the project which, alone or in combination with other plans or projects, can affect the conservation objectives of the protected site.
The exercise must use the best scientific knowledge in the field. A bare conclusion that the site will not be adversely affected is not enough.
The assessment must address the habitats and species for which the site is protected
The appropriate assessment must contain a sufficiently complete examination of the habitat types and species for which the site was designated where they may be affected by the project.
The authority’s findings and conclusions must be complete, precise and definitive enough to remove reasonable scientific doubt about the effects identified.
Effects outside the protected-site boundary can still matter
Holohan is especially important because the legal assessment is not confined by the line drawn around the protected site on a map.
If a project may affect a habitat type or species outside the site and that effect could in turn affect the conservation objectives or integrity of the protected site, the implications must be examined in the appropriate assessment.
The practical question is the ecological connection to the site’s conservation objectives, not merely whether the affected feature lies inside or outside the boundary.
Other habitats and species may need examination where they influence site integrity
The assessment may also need to consider habitat types and species present on the site which were not themselves the reason for designation where effects on those features are liable to affect the protected habitats, species or conservation objectives.
This reinforces the need for an ecological assessment based on how the protected site actually functions rather than a mechanical list of designated features.
Alternatives belong to a different legal exercise
Holohan also dealt with environmental assessment and alternatives. Article 6(3) itself is concerned with whether adverse effects on site integrity can be ruled out. It does not turn the appropriate-assessment stage into a general search for alternative projects.
Where the Article 6(3) test cannot be satisfied, the separate derogation route under Article 6(4) raises questions about alternative solutions, imperative reasons of overriding public interest and compensation.
Holohan sits with Sweetman and People Over Wind
The three cases are best read together. Sweetman explains adverse effect on site integrity and the no-reasonable-scientific-doubt standard. People Over Wind prevents mitigation being used to avoid appropriate assessment at screening. Holohan explains the breadth and quality of the assessment once that stage is reached.
For current UK practice, see our Habitats Regulations Assessment guide.
Read the full Holohan judgment
The full Court of Justice judgment is held in the Planning Geek case law library. Gold Members can open the protected PDF below.
Holohan Appropriate Assessment Case Law Page Updated: 10th September 2026