The Commerce Clause is so important because it might be Congress’ greatest control over what occurs in various states throughout the country. In other words, it is probably Congress’ greatest power. Congress’ ability to “regulate commerce” has proven to be a very important way in which the federal government regulates the states. Congress has used the power of the Commerce Clause, for example, to pass laws prohibiting racial discrimination in local restaurants, such as in the famous decision in Katzenbach v. McClung (1964; see LegalSpeak, p. 26). More recently the U.S. Supreme Court ruled in Gonzalez v. Reich (2005; see LegalSpeak, p. 28) that Congress validly exercised its Commerce Clause powers when it passed the Controlled Substances Act, which criminalized marijuana even in those states that had allowed medicinal uses of marijuana.