Actually... 

This argument assumes that when a substance is criminalized, it is more difficult to access, which is simply not true: high school students under 18 years of age in the United States, for example, report that they can acquire marijuana more easily than they can acquire alcohol¹. This argument also presupposes that legalizing a substance will result in high rates of use, while criminalizing it will result in lower rates. Yet in Holland, where marijuana is legal, only 28 percent of 10^th graders report having used it, while in the U.S., where penalties apply even to possession, 41 percent of 10^th graders say they have used marijuana².