The federal government hasn’t done enough to protect a rare species of whale from lethal entanglement in lobster fishing gear, and new rules are needed to protect the species from extinction, a judge has ruled.

The government has violated both the Endangered Species Act and the Marine Mammal Protection Act by failing to protect the North Atlantic right whale, U.S. District Judge James Boasberg ruled on Friday. The whales number less than 340 in the world and have been declining rapidly in population in recent years.

Boasberg’s ruling was a victory for conservation groups that have long sought to save the whale and a new challenge for lobster fishermen who have fought back against tightening restrictions on where and how they can fish. Boasberg ruled that the court’s findings “do not dictate that it must immediately shutter the American lobster fishery,” but instead said the parties must propose potential remedies to the threat faced by whales.

The ruling “may seem a severe result for the lobster industry” and the government, but no one “operates free from the strict requirements imposed by the MMPA and ESA,” Boasberg wrote.

Environmental groups celebrated the ruling, while some members of the fishing industry took a more measured approach.

The ruling came after a group of environmental organizations sued the federal government with a complaint that it wasn’t doing enough to save whales from lobster gear. Boasberg’s ruling validates that claim, said Kristen Monsell, an attorney for the Center for Biological Diversity, one of the groups that sued.