But because this Court concludes that the Court of Appeals erred as to mootness, this Court has an obligation to assure itself that FOE had Article III standing at the outset of the litigation. An association has standing to bring suit on behalf of its members when its members would have standing to sue in their own right, the interests at stake are germane to the organization's purpose, and neither the claim asserted nor the relief requested requires individual members' participation in the lawsuit. The relevant showing for Article III standing is not injury to the environment but injury to the plaintiff. Here, injury in fact was adequately documented by the affidavits and testimony of FOE members asserting that Laidlaw's pollutant discharges, and the affiants' reasonable concerns about the effects of those discharges, directly affected those affiants' recreational, aesthetic, and economic interests. For a plaintiff who is injured or threatened with injury due to illegal conduct ongoing at the time of suit, a sanction that effectively abates that conduct and prevents its recurrence provides a form of redress.
Civil penalties can fit that description.
Insofar as they encourage defendants to discontinue current violations and deter future ones, they afford redress to citizen plaintiffs injured or threatened with injury as a result of ongoing unlawful conduct. Steel Co . A defendant's voluntary cessation of a challenged practice ordinarily does not deprive a federal court of its power to determine the legality of the practice. If it did, courts would be compelled to leave the defendant free to return to its old ways. United States v. Concentrated Phosphate Export Assn.