In response to widespread brown- and black-outs, Congress passed the Energy Policy Act in 2005. Under this Act, the Department of Energy must conduct a nationwide study of congestion in transmission lines every three years. Because the results of these studies may affect rights traditionally reserved to the states, DOE must prepare each study in consultation with affected states. In California Wilderness Coalition v. U.S. Department of Energy, the Court of Appeals for the Ninth Circuit held that DOE failed to consult with affected states and applied a broad test to find an error that violated the harmless error doctrine. The dissent would have applied a more technical test thus concluded that a harmless error occurred. This Comment explores various harmless error tests and suggests that litigation on this issue would be more predictable if the Supreme Court were to provide additional guidance for substantive and procedural errors.