Greenpeace has lost another attempt to reverse a government ban on "pair trawling" off Devon and Cornwall.
Dolphins can become trapped in pair trawling nets
The ban, up to 12 miles (19km) offshore, was aimed at protecting dolphins from drowning after being caught in nets slung between trawlers.
But the environmental group, which wants a total ban, said fishermen would simply move to deeper waters.
The High Court threw out the case on 10 October, and Greenpeace lost again in the Court of Appeal on Tuesday.
Lords Justices Mummery, Laws and Wall rejected Greenpeace's renewed claim that Fisheries Minister Ben Bradshaw's decision was irrational.
Greenpeace had said the number of dolphins killed in the nets would increase as fishermen went further offshore to evade the ban.
But lawyers for the Department for the Environment Food and Rural Affairs said those fears had proved to be unsubstantiated since the fishing ban was introduced a year ago.
The court heard dolphin deaths outside the 12-mile zone had in fact decreased.
It claims hundreds of dolphins are killed in nets of British and French trawlers every year.
Greenpeace fears "pair trawling" could lead to the common dolphin being wiped out in the English Channel.
Greenpeace campaigner Willie Mackenzie said after the ruling that the ban was a "hollow political gesture".
"Greenpeace's campaign to get the UK Government to take real action to protect dolphins will continue," he said.