External effects increase. When drug use increases, the negative externalities imposed upon others also increase. There will be more third-party victims because more people are choosing to use drugs. Rightly or wrongly, the United States has taken the approach that drug use is a crime and must be prohibited. There seems to be few positive results.
Drug use is common and on the rise among young people.
Success depends upon the ability of the government to curtail production directly or to stop the inflow of drugs to US markets. Since most production of the harder drugs occurs outside U.S. borders, we have very limited influence over direct production. But the problem is that production can easily be concealed by going underground. We may catch some of the distribution, but only a small fraction. Even if one distribution chain is cut down, another one will likely appear because of the big profits to be made.