How have courts interpreted the harmless argument in federal forfeiture cases?

argument, the court would find the constitutional error not harmless]; United States v. Montgomery (8th Cir.1996) 100 F.3d 1404, 1407 [stating the government's failure to raise harmless error in its brief waived the argument on appeal but, exercising its discretion to overlook the waiver and review the record on its own motion, court concluded the error was not harmless]; United States v. VarelaRivera (9th Cir.2002) 279 F.3d 1174, 1180 [stating the government did not argue that the error was harmless and this failure waived the argument]; United States v. Vallejo (9th Cir.2001) 237 F.3d 1008, 1026 [same, adding that nevertheless, under the circumstances of the case the error was not harmless].) Furthermore, most of these courts explicitly recognize that they retain discretion to review the record and decide whether any error was harmless even when the government fails to make the argument. This recognition undermines any contention that the forfeiture rule applied by federal courts is constitutionally mandated.