This handbook for planners was conceived by planners and lawyers in the summer of 1987 in the wake of the U.S. Supreme Court's important land use decisions in Keystone, First English, and Nollan which, incidentally, coincided with our country's bicentennial celebration of the U.S. Constitution. The book's purpose is to provide professional and citizen planners with a practical, usable guide to federal constitutional principles for land use planning practice. In short, it is a response to Justice Brennan's exhortation in San Diego Gas and Electric Co. v. City of San Diego, 450 U.S. 621, 655 n.26 (1981), (Brennan, J., dissenting) that planners as well as policemen should "know the Constitution." Some planners may not agree with Brennan's equation of the extent of policemen's and planners' responsibilities in the constitutional arena. However, there is no doubt that the Supreme Court's recent decisions have motivated planners to know the constitutional limits of the regulatory programs that they propound—to avoid what one planner described as "the feeling of walking backwards toward a cliff."