Editors' Summary: In June, the Supreme Court handed the Environmental Protection Agency's Clean Air Act enforcement program a significant victory. The Court held that EPA is not required to act on a proposed SIP revision within four months and is not barred from enforcing the existing SIP if it does not act on the proposal within a reasonable time. This Comment describes the "four-month rule" for revisions and the enforcement bar that created the split in the circuits, and it analyzes the opinion. The author notes that the opinion creates confusion concerning the remedy for agency delay and argues that the proper remedy lies with the courts of appeals.