US District Judge Maxine Chesney rejected an argument by the Center for Biological Diversity that the Coast Guard should comply with the Endangered Species Act when it regulates ship traffic. Chesney issued a summary judgment Monday in San Francisco.

In her decision, Chesney said that the Coast Guard's daily management of shipping traffic does not by itself trigger Endangered Species Act requirements. The environmental group failed to show that the agency is engaged in any specific action that would require it to initiate such measures, the judge said.

Andrea Treece, an attorney for the environmental group, said her client has not decided whether to appeal the decision.

"It's unfortunate the judge took such a narrow view of what was before her," she said.

Stephanie Young, spokeswoman for the Coast Guard in Los Angeles, said they don't comment on legal decisions but added that the agency takes protecting marine animals seriously. Following the whale deaths that prompted the lawsuit, the Coast Guard conducted aerial monitoring of whales and recommended that mariners reduce their speeds in the Santa Barbara Channel.

The lawsuit was filed after three of the endangered mammals were confirmed to have been hit by ships and another two whale carcasses were also spotted in 2007. The incidents around the channel caught the group's attention because the death toll was much higher than the acceptable level for non-natural whale deaths, said Treece, who called the deaths "heart-stopping."

Less than 10,000 blue whales are left in the world's oceans after being reduced by whaling.

Blue whales normally pass through the channel on their way to feed in grounds further north and are usually gone by the end of August. In 2007, however, a large number of whales stayed to feed in the channel, which holds some of the busiest shipping lanes in the world.