In the United States v. W.T. Grant Co., et al., 1952, the Supreme Court ruled on a case involving voluntary cessation of allegedly illegal conduct by defendants who were charged with violating antitrust laws. The court held that a defendant's voluntary cessation of alleged misconduct does not necessarily deprive a federal court of its power to determine the legality of such behavior, especially when there is no assurance that it will not be repeated in future. This ruling was based on public interest and necessity for judicial protection against potential harm from recurrence of unlawful activities. Therefore, even if an offending party ceases their illegal actions voluntarily, they may still face legal consequences unless they can prove beyond doubt that "there is no reasonable expectation" or "demonstrable proof" that these actions won't recur.

In the dissenting opinion for United States v. W.T. Grant Co., Justice Jackson argued that the majority's decision to allow a voluntary cessation of allegedly illegal conduct as sufficient grounds to dismiss an injunction was flawed. He contended that this ruling could potentially encourage companies to temporarily halt unlawful activities only until legal scrutiny subsides, then resume them later on without any real consequences or deterrents in place. Furthermore, he expressed concern over the court’s reliance on mere assurances from defendants about their future behavior rather than concrete evidence of change or regulatory oversight mechanisms being implemented. This approach, according to Justice Jackson, undermines both public trust and confidence in judicial processes by allowing corporations too much leeway when it comes to compliance with laws and regulations.