A controversial cull of seagulls aimed at lowering the risk of bird strike to aircraft in Lancashire has been blocked by the Court of Appeal.
The government approved the killing of hundreds of lesser black-backed gulls in 2013 because of safety fears at an airfield in the Ribble Estuary.
Operations to control the number of herring gulls were also authorised.
But the culling has now been blocked after a campaign by the Royal Society for the Protection of Birds (RSPB).
BAE Systems had requested the culls to reduce the risk of birds coming into contact with aircraft operating at the company's Warton aerodrome.
Last year the High Court dismissed the RSPB's claim the culls were unlawful and would set a "deeply disturbing precedent" when the seabirds were in "substantial decline".
But three appeal judges have unanimously overturned the High Court's decision.
They ruled former environment secretary Owen Paterson's original decision to grant the culls was "fatally flawed" and quashed it.
Lord Justice Sullivan acknowledged the affected birds nested in a special protection area (SPA) under the EU Directive on the Conservation of Wild Birds.
He said Mr Paterson had "misinterpreted the conservation objectives of the SPA".
The judge ruled the minister had wrongly considered the number of birds left would remain favourable for breeding and conservation purposes, and the cull would not adversely affect the integrity of the site.
The RSPB said it accepted the risk to aircraft but questioned the legality of killing birds without acknowledging the impact of removing "almost a fifth of the breeding population of a species on a protected site".