A European Court of Justice ruling against a proposed Galway bypass has been described by An Taisce as “a huge leap forward for nature conservation, not only in Ireland but across the EU”.

In its judgment yesterday, the court ruled that permission may not be given for developments on priority conservation sites where there is a risk that it will bring about “the disappearance or the partial and irreparable destruction of the protected site”.

The 14-page judgment by the court ruled on three questions referred to it by the Supreme Court on the relationship between infrastructure applications and areas designated as environmentally-sensitive under the EU habitats directive.

Galway West Fine Gael TD Sean Kyne has signalled that the planning authorities may make a new application for the outer bypass, citing overriding public interest.

Under article 6 (4) of the EU habitats directive projects which may have an adverse impact on the integrity of a designated site may go ahead on grounds of “imperative reasons of overriding public interest (IROPI)”.

Fianna Fáil TD Éamon Ó Cuív has urged the Government to take”"immediate” action to secure the project through the IROPI clause.

Welcoming the ruling as a “landmark judgment”, An Taisce’s natural environment officer Andrew Jackson said its “beneficial conservation impacts” would apply to a total of 72 EU priority habitats, of which 16 are located in Ireland.

Friends of the Irish Environment said: “This ensures that problems we have had with cases like raised bogs – the ‘death by a thousand cuts’ – must no longer be permitted. Even the partial destruction of protected areas may not be permitted.”

The Galway bypass would have resulted in the loss of 1.47 hectares of limestone pavement in the Lough Corrib Natura 2000 site, which covers 270 hectares. The court’s judgment, in a case brought by environmental activist Peter Sweetman, also confirmed that it is not necessary to prove that a project would lead to “irreparable destruction” as the precautionary principle should be applied.

The British and Greek governments had intervened in the case, fearing that such a strict interpretation of EU conservation law would inhibit their own development projects, but ended up “on the losing side”, as Mr Jackson noted.

The case now reverts to the Supreme Court in Dublin, which must apply the European court’s ruling in determining whether An Bord Pleanála’s decision in November 2008 to approve the bypass should now be quashed.