Marshall reasoned that the Constitution places limits on the American government's powers, and that those limits would be meaningless unless they were subject to judicial review and enforcement. He reasoned that the Constitution's provisions limiting Congress's powersuch as the export tax clause, or the prohibitions on bills of attainder and "ex post facto" lawsmeant that in some cases judges would be forced to choose between enforcing the Constitution or following Congress. In his opinion, the dilemma was not difficult: "The question whether an act repugnant to the Constitution can become the law of the land is a question deeply interesting to the United States, but, happily, not of an intricacy proportioned to its interest." He held "virtually as a matter of iron logic" that in the event of conflict between the Constitution and statutory laws passed by Congress, the constitutional law must be supreme. Again borrowing from Federalist No. 78, Marshall stated: