Federal Practice Manual for Legal Aid Attorneys: 2.8.3 Doctrinal Foundations
The Supreme Court limited the ability of federal courts to enjoin or otherwise to interfere with state judicial proceedings in Younger v. Harris and subsequent decisions. In Younger, plaintiffs sought a federal injunction against a state criminal prosecution on the ground that the state statute alleged to have been violated was unconstitutionally vague. The Court held that such an injunction could be granted only in extraordinary circumstances to prevent immediate irreparable injury.