Greenhouse gas emissions from transportation in the United States have remained persistently high. One cause is common low-density land use patterns that make most Americans dependent on automobiles. Reducing these emissions requires increasing density, which U.S. local government law makes difficult to achieve through the political process. This article argues that Mount Laurel, a 1975 New Jersey Supreme Court case that addressed an affordable housing crisis by restraining local parochialism, provides a potential solution. It demonstrates that a Mount Laurel-style challenge to low-density zoning is legally and normatively defensible in New Jersey and other states.