Congress increasingly has enacted cooperative federalism programs to achieve complex regulatory policy objectives. Such programs combine the authority of federal regulators, state regulators, and federal courts in creative and often pathmarking ways, but the failure of these actors to appreciate fully their respective roles threatens to undermine cooperative federalism’s effectiveness. In this Article, Professor Philip Weiser develops a coherent vision of how federal courts should enforce cooperative federalism regulatory programs. In particular, he relates the rise and purpose of cooperative federalism to the federal courts’ increased reluctance to make federal common law under the Erie doctrine and their greater deference to administrative agencies under the Chevron doctrine. Professor Weiser then applies this conception of cooperative federalism to the implementation of the Telecommunications Act of 1996, the most ambitious cooperative federalism venture yet, and shows how federal courts should exercise their authority in coordination with federal and state regulators to advance the Act’s goals.