National Environmental Policy Act (NEPA) litigation is often a tactical exercise. NEPA requires decisionmaking procedures that ensure the full and timely consideration of the environmental impacts of major federal actions. Though NEPA suits are usually waged over procedural points, preserving the integrity of NEPA's procedures is not necessarily the plaintiffs' first goal. Plaintiffs may bring NEPA suits as an indirect means to a more substantive end—to force the agency to abandon what they judge to be a poor proposed action. Such plaintiffs do not expect the court to order the agency to take a better action; they only hope to delay and win reexamination of the bad one.

The worst case analysis regulation,¹ which addresses the procedures for dealing with uncertainties about environmental impacts, has become a dramatic focus of a handful of such tactical actions. In particular, in the cases dealing with pesticide use on public lands in the Pacific Northwest, worst case litigation has been a stunningly effective tool for thwarting Forest Service and Bureau of Land Management (BLM) spraying plans.² Enforcement of the worst case analysis requirement has been an unpleasant surprise to these agencies; they and others fear the same kinds of surprises may lurk in other contexts.