so remain live following cessation of the chal- lenged activity if the actions are capable (1) of repetition and (2) of evading review. See, e.g., Super Tire Engineering Co. v. McCorkle, 416 U.S. 115, 122, 94 S.Ct. 1694, 1698, 40 L.Ed.2d 1 (1974). Finally, the existence of "a public interest in having the legality of