Anti-Injunction Act

The Anti-Injunction Act (28 U.S.C. § 2283), is a United States federal statute that restricts a federal court's authority to issue an injunction against ongoing state court proceedings, subject to three enumerated exceptions. It states:

"A court of the United States may not grant an injunction to stay proceedings in a state court except as expressly authorized by Act of Congress, or where necessary in aid of its jurisdiction, or to protect or effectuate its judgments."

The Act was originally enacted as part of the Judiciary Act of 1793. The current Act was enacted in 1948. As interpreted by the Supreme Court of the United States, the Act is a bastion of federalism and embodies the need to avoid "needless friction" between state and federal courts.