A U.S. Supreme Court case involving medical marijuana use will likely be decided on the legal arguments – not on whether there is any merit to the claim that marijuana is beneficial to those who are in pain. So says Saint Louis University law professor Sandra Johnson, who says the decision can be expected to come down to whether the federal government has a right to exercise its authority to regulate interstate commerce in a California case involving a state in which marijuana use is legal. A ruling in favor of the states does not mean marijuana use would suddenly be legal in Missouri. That would only happen if Missouri passed a state law allowing for the legal use of grass.