A dozen states have adopted legislation in recent years allowing patients with certain illnesses to legally use marijuana as a medicine — measures that clearly conflict with federal anti-marijuana laws. In California, federal drug agents raided the homes of patients using medical marijuana, claiming federal law superceded California's law permitting compassionate use of marijuana. Two medical marijuana users challenged Washington's authority to overrule a state's law, and the U.S. Supreme Court is expected to rule on the case this spring. Meanwhile, some studies show that marijuana is less addictive than caffeine, and legalization proponents argue that it should therefore be available to adults for personal use. The government and other critics continue to insist that marijuana should remain illegal because it is not an effective medicine and is both dangerous in its own right and as a “gateway” drug to cocaine and other more addictive and harmful drugs.