Before the merger of water law and land use planning can occur, local and state regulators need strong guidance from experts in the field, not only in extra-legal fields such as planning, hydrology, geology, engineering, biology, and transportation, but also in mainstream legal areas including legislation (local, state, and federal), administrative law, and enforcement. The purpose of this article is to identify a somewhat unorthodox source of guidance - the United States Supreme Court, specifically the Rehnquist Court from October, 1984, through June, 2005, a period of remarkable stability for the nation’s highest tribunal.