The D.C. Circuit held that EPA must justify emissions limits set for certain hazardous air pollutants. The CAA requires EPA to set limits for seven different hazardous air pollutants (HAPs).

A district court held that New York's Zero-Emission Credit (ZEC) program is not preempted by federal law. In an effort to curb the effects of global warming, New York issued a Clean Energy Standard (CES) Order that created two programs, one being ZEC.

The California Supreme Court held that the state Environmental Quality Act (CEQA) was not preempted by federal law.

The Tenth Circuit held that a mining company has the right to recover cleanup costs at a Superfund site because the U.S. government was an owner under the statute. Over the last century, the mining company and its corporate predecessors mined molybdenum at a site near Questa, New Mexico.