Decriminalizing a drug like marijuana means that it no longer is a crime to possess marijuana for personal use, The advantages of decriminalizing marijuana are so numerous and powerful that it is difficult to understand the intense opposition.

The movement at the state level of the United States to decriminalize various uses of marijuana-especially for “ medical” purposes- has accelerated in recent years. It will not be long before marijuana use for many purposes will be decriminalized in the great majority of states, and I also expect rapid expansion in the number of states that legalize marijuana for all recreational uses. It is much better for states rather than the federal government to decide about the legality of drug use since that would allow some states to continue to treat marijuana use as a criminal offense if they so wish. However, as Posner points out, it becomes harder for some states to criminalize marijuana use when the great majority of states have decriminalized it.

Decriminalizing consumption and some production of marijuana would have large beneficial effects on Mexico. Traditionally, Mexico has produced the majority of marijuana consumed in the US. The distribution of marijuana from Mexico to the US is controlled by powerful drug cartels that have made enormous profits from their trafficking in drugs. The Mexican government’s battles with these cartels have caused tens of thousands of deaths, and wholesale corruption of Mexican police and government officials. The trend toward legalization of marijuana in America is lowering the profitability of Mexican cartels and weakening their hold over the Mexican population.

Many people are unhappy when they are addicted to drugs, be it alcohol, nicotine, cocaine, or marijuana. They would like to free themselves from their addictions, but that is not easy to do by the definition of what an addiction means. This is especially difficult for addictions to illegal substances. Clinics are reluctant to treat individuals who are addicted to substances that are illegal to consume, groups like AA are more difficult to form and thrive, and informal support group also face many obstacles.

Critics rightly claim that decriminalizing marijuana is likely to encourage experimentation with marijuana use, and probably will increase total consumption (although see our discussion of taxes in the following paragraph). However, what is more important, decriminalization will tend to reduce the rate of addiction to marijuana. The reason is that decriminalization will encourage the development of more clinics that treat this addiction, will help spread the growth of Marijuana Anonymous organizations that help addicts break their addictions, and will produce other efforts to combat severe addictions to marijuana. As a result, while marijuana use may go up, the number of addicts is likely to go down. This should allay the fears of many opponents of decriminalization that it would lead to a large expansion in the number of addicts.

Decriminalizing marijuana paves the way for taxing its use, in the same way that alcoholic consumption became rather heavily taxed after the end of Prohibition. The higher the tax rate, the higher the retail price of marijuana, and hence the lower would be its consumption. So replacing the present situation with significant taxes on the legal consumption of marijuana could end up lowering the demand for marijuana, despite the effects of decriminalization on experimentation with marijuana.

The present spending of substantial resources on trying to combat marijuana use would be replaced by considerable revenue from taxing its use. That potential revenue is a temptation of many strapped state governments to decriminalize marijuana. Of course, if the tax rate were too high, some of the marketing of marijuana would move underground to try to escape the tax. However, experience with other goods that are heavily taxed, including alcohol, shows that the advantages of legal sale and purchase of a substance like marijuana are so large that the tax rate could be rather high without a large fraction of the sales going underground.

A good use of the tax revenue would be on education and other efforts to point out the harm from becoming addicted to drugs. Some of the revenue could also be used to support drug clinics and other private groups that are trying to both treat addictions and to discourage individuals from becoming addicts. These are far better uses of government revenues than are the expenditures on police, courts, and prisons to apprehend and punish individuals who consume marijuana.