In Leary v. United States, 395 U.S. 6, 89 S. Ct. 1532, 23 L. Ed. 2d 57 (1969) the defendant was convicted of "transporting" or "concealing" within the United States imported marijuana with the defendant "knowing" the marijuana had been imported into the United States. See id. The statute provided a presumption that the defendant knew the marijuana had been imported into the United States from the defendant's mere possession of the marijuana. See id. After concluding that most marijuana users do not know where their marijuana comes from, the Supreme Court decided the presumption was unconstitutional. See Leary, 89 S. Ct. at 1545-57, 1557. Consistent with the "teaching of Stromberg," the problem in Leary was that the "knowledge" presumption made criminal conduct that did not constitute the crime as defined by the statute. See Leary, 89 S. Ct. at 1557.