That is one dumbest comments I have read here. The law deters acts. The tougher the law, the more deterrent.
Countries and states that have decriminalized pot have seen dramatic increase in its usage:
http://www.sarnia.com/GROUPS/ANTIDRUG/argument/myths.html
Dr. K. F. Gunning, president of the Dutch National Committee on Drug Prevention, cites some revealing statistics about drug abuse and crime. Cannabis use among students increased 250 percent from 1984 to 1992.
Decriminalizing marijuana in Alaska and Oregon in the 1970s resulted in the doubling of use.
California decriminalized marijuana in 1976, and, within the first six months, arrests for driving under the influence of drugs rose 46 percent for adults and 71.4 percent for juveniles.