Winter v. Natural Resources Defense Council, Inc., 555 U.S. 7 (2008)

In its training exercises at sea, the U.S. Navy uses modern sonar to detect and follow enemy submarines. This technology, which has been used for 50 years, is based on emitting pulses of sound underwater and then receiving acoustic waves that echo off the target. Although this has been established as the most effective way to identify submerged submarines that are within torpedo range, the use of active sonar arguably harms marine mammals. They may be subject to hearing loss, decompression sickness, and behavioral disruptions when the technology is used. The Secretary of Defense is allowed under the Marine Mammal Protection Act of 1972 to exempt an activity that harms marine mammals if it is deemed necessary for national defense, and the Navy had received such an exception for this case. Under the National Environmental Policy Act of 1969, moreover, federal agencies must compile an environmental impact statement for any major federal action that significantly affects the quality of the human environment. This requirement may be avoided only if the agency uses a shorter environmental assessment to determine that its proposed action will not have a significant impact on the environment. The Navy believed that this exception to the requirement applied, and it issued an environmental assessment in support of that conclusion. The Natural Resources Defense Council sued the Navy to prevent its use of sonar in training programs. The Council received a preliminary injunction in federal court.

Whether the Navy's use of mid-frequency active sonar during training exercises requires an environmental impact statement under the National Environmental Policy Act, given the potential harm to marine mammals.

The judgment is modified to allow the provisional conditions to remain in place until the Navy’s completion of an acceptable EIS.

This unusual grant of certiorari for a dispute over a preliminary injunction allowed the Supreme Court to emphasize the importance of the national security interest attached to the Navy's training program. Even if the lower court eventually found on the merits that the Navy had violated a law, it probably could not impose a permanent injunction because of this national security interest.