Residents objecting to the planned €320m runway at Dublin Airport are "absolutely gutted" that the Supreme Court has refused to hear their appeal.
A three-judge division of the Supreme Court has determined that the concerns raised by 22 residents over the decision to expand the airport were not an issue of public importance.
The small town of St Margaret's is located adjacent to the site of the proposed runway.
For over 20 years, the St Margaret's Concerned Residents group was vocal in opposition to the runway and the noise that would be created.
The residents had challenged the decision of Fingal County Council to extend what had been a 10-year permission to develop the airport.
They claimed they were excluded from the extension decision and that development work on the site had commenced without proper compliance to the permission granted.
In its determination, the Supreme Court said the High Court had found the proceedings were an "impermissible collateral attack" on the original planning permission process, which the residents had fully participated in.
It was "no more than a bare assertion unsupported by evidence", and this cannot be said to raise an issue of general importance, the Supreme Court ruled.
Sheila Morris, secretary of the Concerned Residents group, told the Herald that "disappointment doesn't even come close" to what they are feeling.
"It's a disgrace - we're absolutely gutted," she said.
"The decision is a slap in the face to all the residents who have been fighting against this development for over 20 years.
"Generations have lived in these homes and to be directly adjacent to this new runway will be a constant burden on our community."
Despite the court's ruling, Ms Morris said the fight against the expansion is far from over: "We will be continuing our campaign because up to now our genuine concerns haven't been dealt with by anyone."
The runway, due to be finished by 2021, has been planned for since the late 1960s.