The U.S. Supreme Court case Zwickler v. Koota, 1967, dealt with the issue of whether a federal court could decide on the constitutionality of a state law when there was no immediate and real threat to enforce that law against the plaintiff. The petitioner, Zwickler, had previously been convicted under New York State's election laws for distributing anonymous political leaflets and sought declaratory relief from future prosecution under these laws in Federal District Court. However, his request was denied by both lower courts due to lack of jurisdiction over state matters as well as mootness since he wasn't currently facing any charges under this statute. In its decision, the Supreme Court reversed these rulings stating that federal courts have an obligation to hear cases where constitutional rights may be violated even if it involves adjudicating upon state statutes' validity; they cannot avoid their responsibility citing abstention doctrine or mootness principle unless there is absolutely no chance of recurrence of such violation in future.

In the dissenting opinion for Zwickler v. Koota, Justice Harlan argued that the case should have been dismissed due to mootness as there was no longer a live controversy at stake. He pointed out that since Zwickler had not indicated any intention of distributing similar handbills in future elections, his claim did not meet the requirement of "capable of repetition yet evading review." Furthermore, he disagreed with the majority's decision to rule on constitutional grounds when it could have been decided based on state law principles. This approach violated long-standing judicial restraint principles which dictate avoiding unnecessary rulings on constitutional issues. Lastly, Justice Harlan criticized the Court’s willingness to intervene in state criminal proceedings without sufficient justification and warned against undermining federal-state relations by doing so.