The article is an entry in a long-standing debate concerning the soundness of the state action principle in American constitutional law. According to that principle, exercises of private rights by private people are not subject to the constitutional rules that apply to the government, even though those private decisions are supported by the government's coercive power. For many decades, some scholars have argued that the principle is irrational and also inconsistent with the purpose of some of the constitutional norms that it limits, such as the First Amendment. The article defends the principle from its critics, a group that includes a number of important contemporary constitutional theorists. We maintain that the state action principle is a reasonable implementation of the Constitution's basic distinction between public and private decision makers, and that it is consistent with a plausible and we think persuasive, understanding of the particular constitutional rules that the critics maintain the state action principle arbitrarily limits.