are put on notice that changes may occur to duties until liquidation or reliquidation of entries at issue. See 19 U.S.C. § 1500; Dart Exp. Corp. v. United States, 43 C.C.P.A. 64, 76 (1956). “No vested right to a particular classification or rate of duty or preference is acquired at the time of importation.” N. Am. Foreign Trading Corp. v. United States, 783 F.2d 1031, 1032 (Fed.Cir.1986) (citing Norwegian Nitrogen Prods. Co. v. United States, 288 U.S. 294, 318, 53 S.Ct. 350, 77 L.Ed. 796 (1933)). In cases involving importers’ challenges to the application of new laws based on retro-activity, the courts have looked at liquidation as the relevant “past event” with respect to the operation of a new rule. See, e.g. Travenol Labs., Inc. v. United States, 118 F.3d 749, 753 (Fed.Cir.1997) (<HOLDING>); Syva Co. v. United States, 12 CIT 199, 204,
recognizing that the application of a retroactive amendment is discretionary holding retroactive application holding no retroactive application holding iiriras preclusion of application for relief constitutes a new disability and is impermissibly retroactive holding that liquidation or reliquidation of entries is the triggering or operative event for deciding whether application of statute or regulation is impermissibly retroactive