In June, President Obama signed an executive order that vastly expands the Pacific Remote Islands Marine National Monument. It will create the world’s largest marine reserve, placing 782,000 square miles of ocean off-limits to commercial fishing and oil and gas exploration.

But perhaps not off-limits to U.S. Navy sonar exercises.

When President George W. Bush designated the Northwestern Hawaiian Islands Marine National Monument in 2006 and the Marianas Trench Marine National Monument in 2009, he also granted the U.S. Navy an exception to the ban on environmentally destructive activities inside these sanctuaries. This special “carve-out” allows the Navy to conduct antisubmarine sonar trainings inside the marine equivalents of national parks.

Now is the time for President Obama to step up and designate this expanded national monument as a true sanctuary for vulnerable marine life. At highest risk are the deep-diving whales that are ubiquitous in these pristine waters. These whales have repeatedly mass-stranded in the wake of high-intensity naval sonar exercises around the world.

A few months ago, during joint antisubmarine exercises among the U.S., Israeli, and Greek navies, at least five beaked whales stranded and died on the coast of Crete. As graphic photographs of dead whales in the bloody shallows circulated on the Internet, a team of Greek veterinary pathologists rushed to the scene to retrieve fresh organ samples for analysis. The autopsies found hemorrhaging inside the whales’ internal organs, bleeding from the ears, and tissue evidence of decompression-like sickness seen in other deep-diving whales following rapid ascent. They echo the grim reports from prior mass strandings linked to naval war games in the Caribbean, the Mediterranean, and elsewhere. Given the history of sonar strandings in the region, some Greek biologists have despaired at the fate of that population of whales.

As I recount in my new book, War of the Whales, the Navy’s conflict with whales reached the courtroom years ago, when environmentalists began challenging the use of whale habitats for training exercises with sonar and explosives. The Natural Resources Defense Council first went to court in 1994 to prevent the Navy from detonating 10,000-pound bombs during “ship shock” tests in the whale-rich Channel Islands National Marine Sanctuary off the California coastline. In the years that followed, NRDC filed a series of lawsuits under the Marine Mammal Protection Act and other federal statutes to limit the Navy’s sonar trainings in areas of vital importance to whales.

After suffering a string of court losses and being repeatedly found in violation of federal conservation laws, the Navy agreed to conduct comprehensive environmental impact statements on all of its U.S. coastal ranges and to implement some risk reduction procedures during exercises. The Navy does not, however, perform comprehensive environmental reviews prior to exercises in foreign waters—which may explain why strandings like those on Crete are still occurring. And on the Navy’s U.S. ranges, some whale populations are showing signs of decline, leading NRDC and another environmental group, Earthjustice, to file suit this year to halt Navy exercises off the California and Hawaii coasts.

This week marks the beginning of the massive Rim of the Pacific war games hosted by the U.S. Pacific Fleet in Pearl Harbor, Hawaii. These monthlong joint exercises deploy 47 warships from 22 foreign navies, six submarines, more than 200 aircraft, and 25,000 sailors. Ten years ago, during 2004 RIMPAC exercises involving high-intensity sonar, 200 melon-headed whales panicked and fled into Hanalei Bay. Citing this incident, NRDC went to court in 2006 and won an emergency injunction that delayed the start of that summer’s RIMPAC war games until the U.S. Navy agreed to limitations on its sonar exercises.

This year’s ramped-up RIMPAC exercises highlight the Obama doctrine’s pivot toward Asia. But projecting a more robust U.S. naval presence in the Pacific threatens to undermine the conservation goals of the Pacific Remote Islands Marine National Monument. The islands were once home to two U.S. naval air stations, and although there are few large Navy trainings conducted in these waters today, ships in the area may engage in sonar testing. The only current restriction on Navy sonar operations is a 12-nautical-mile limit surrounding the islands—and only for low-frequency sonar. Mid-frequency sonar exercises—the kind of sonar implicated in the recent Crete strandings—have no limitations. Michael Jasny, the director of NRDC’s Marine Mammal Protection Project, estimates that 99.6 percent of the newly expanded national monument is currently unprotected from naval sonar.

The Navy hasn’t always been indifferent to whales. Beginning in the early 1960s, the U.S. Navy captured and trained dolphins, orcas, and other small cetaceans to patrol harbors for enemy swimmers, retrieve unexploded armaments from the ocean floor, and sweep harbors for live mines in Vietnam. In 1986, Navy dolphins were first deployed in the Persian Gulf to patrol the harbor in Bahrain to protect U.S. flagships from enemy swimmers and mines and to escort Kuwaiti oil tankers through potentially dangerous waters. In 2003, during Operation Enduring Freedom, Navy-trained dolphins and sea lions were redeployed to clear mines near the Iraqi port of Umm Qasr and other locations.

For decades, the Navy has also studied whales’ exquisitely refined biosonar in hopes of reverse-engineering it to improve the Navy’s own surveillance of enemy submarines in dark ocean depths. It’s a cruel irony that the Navy’s modern, high-intensity sonar—partly derived from its extensive research into cetacean biosonar—causes mass strandings of certain species of whales.

In the years since losing its first court case over sonar exercises, the Navy has agreed to spend tens of millions of dollars studying the behavioral responses of deep-diving whales to high-intensity sonar. There is now consensus among researchers—including those funded by the Navy—that whales are acutely sensitive to acoustic disturbances. Sonar and other sources of ocean noise provoke a range of lethal and nonlethal responses, including abandoning their foraging habitats and diverting their migration paths. And the stress of chronic noise pollution responses can threaten whales’ often fragile reproductive health.

Given this growing body of evidence, one wonders why the Navy continues to insist on conducting sonar trainings in whale habitats, even at the risk of turning would-be sanctuaries into death traps. Why must whales continue to die for military practice?

Despite their highly evolved social structures and their prodigious talents for communication and navigation, whales don’t grasp the fine points of territorial limits, laws of the sea, and national monument designations. They can’t escape the underwater cacophony from transcontinental shipping, offshore oil and gas drilling, and military sonar that have combined to make their marine habitats unbearably noisy.

The U.S. Navy has repeatedly failed to conduct sonar trainings without harming federally protected marine mammals. And as judges in virtually every circuit have ruled, regulators at the National Oceanic and Atmospheric Administration have failed to hold the Navy accountable to the law. Now is the time for citizen action, during the summerlong public comment period before the fine-print rules are finalized. Comments should be directed to the secretary of Commerce and the secretary of Interior. It will then fall to the commander in chief to finally grant the whales a sanctuary from the Navy’s acoustic storm. He should begin with the Pacific Remote Islands Marine National Monument.