Fishermen in the western Japanese town of Taiji corral the dolphins before killing many for meat in a hunt that has long been a source of controversy and was featured in the Oscar-winning documentary "The Cove."
Critics of this year's hunt included Caroline Kennedy, the U.S. ambassador toJapan.
The lawsuit, which activists said is the first launched on behalf of the dolphins, said that the Taiji Whaling Museum prevents environmental activists and dolphin experts from entering, thereby violating the Japanese constitution, and demanding some 6.7 million yen ($65,800)in compensation.
The main reason experts want access to the museum is to check on the condition of a rare, one-year-old albino dolphin captured during the hunt in January and kept in an aquarium there with other dolphins, said Ric O'Barry, one of the stars of "The Cove", at a news conference in Tokyo.
"She's ... a symbol of the hundreds of thousands of dolphins that have been slaughtered needlessly in that cove," O'Barry said, noting that thousands of other dolphins have been shipped all around the world due to demand from aquariums.
He called for the dolphin, nicknamed Angel, to be moved outdoors, saying that her current indoor tank is dark and crowded with too many other dolphins, producing stress that could damage her health.
"Saving Angel, bringing attention to her, worldwide attention... could end the traffic and captivity of dolphins from Taiji, and stop the slaughter," he added. "That is our hope."
Releasing Angel into the ocean is considered to be too risky as her pod had been migrating when it ran into the hunt, and as a lone dolphin her chances of survival would be slim, especially given her age.
Sarah Lucas, the CEO ofAustraliafor Dolphins and a plaintiff in the lawsuit, said that she was shown a sign saying that people against whaling were unwelcome in the museum and denied entrance when she visited in February. She said she believed the lawsuit would open the door for others.
Taiji came into the spotlight after the 2009 release of "The Cove", directed by former National Geographic photographer Louie Psihoyos. It shows the hunt in grisly detail and calls for an end to commercialfishingof marine mammals.
Fishermen say the cull is a traditional part of their livelihood in an area that has hunted dolphins and whales for thousands of years.
In an unusual move, U.S. ambassador Kennedy in February said she was deeply concerned by the hunt.
Taiji Whaling Museum vice director Tetsuo Kirihata said that the museum did try to keep activists out and confirmed that Lucas had been denied entrance, but said the move was not discriminatory or based on appearance and that anybody who said they were a tourist could come in.
"Taiji is full of activists expressing their opposition to the hunt and to keeping dolphins in captivity," he told Reuters. "If we let them in, they would disturb our other visitors and interfere with our business."