Suppose the federal government were to cap nationwide speed limits at 40 m.p.h. with the honorable goal of greatly reducing crash fatalities. They reason that being a little late is small price to pay for saving lives, and the public reluctantly agrees.

Years later, you may have teens tell you in surveys that they drive slower, and some federal agencies will ask that you see that as proof the law is doing good, but look at the overall societal consequences of the law:

• it would be grossly disobeyed, criminalizing a huge percentage of the population, including teens, and in result many more drivers would end up unlicensed and uninsured
• it would lower the public’s respect for law enforcement and the law would be mocked in pop culture
• some officers would abuse the law via selective enforcement to search cars, build citation revenue, or arbitrarily punish individuals with, e.g., disliked political stickers or fashion
• other officers would complain that the law was ineffective and was diverting resources from the pursuit of more serious crime
• over time, punishments would be made more severe in efforts to “crack down”, but “speed abuse” whether it be at 90 m.p.h. or 50, would continue
• private prisons, mandatory driving schools, and insurance companies (more speeders means higher rates) would grow enormously and spend millions lobbying against efforts to raise the limit
• people with legitimate urgency (e.g. rushing someone to a hospital) would tend to follow the rules out of fear
• states and counties would find ways to tiptoe around the limit or reduce penalties, creating a nation where penalties vary wildly with unfortunate consequences for drivers who speed into the wrong area.
• ironically, fatalities could even go up as speeders and unlicensed drivers–who know they’re risking harsh penalties regardless–see no reason to maintain any safe speed, and when tailed would be more likely to flee to escape those penalties.
• states would campaign for the repeal of the law so they may have their own speed limit decisions back, and eventually repeal would occur

Such a law seems crazy, but we did have one in the U.S. quite recently, the National Maximum Speed Law. In essence it’s the story of the federal criminalization of a behavior the public finds reasonable and acceptable. What changes the shape and severity of this process is the level of public acceptance and awareness of the negative effects caused by the law. An analogous event with even greater negative effects and visibility of them was the Prohibition of alcohol in 1920.

The analogue most nearing the process of completion is the federal prohibition of cannabis. It’s taking longer than usual because opponents of the drug have been very successful at demonizing its effects, marginalizing its users, and suppressing scientific information. Particularly they were effective at extending prohibition to the international level with interlocking treaties, and creating an extensive bureaucracy of federal agencies (in particular the FDA, HHS, NIDA, and DEA) who work together to maintain the status quo. Years ago such a viewpoint would brand you a conspiracy theorist, but here’s an ACLU site with a letter from 38 prominent members of Congress pushing for cannabis to be made easier to obtain for scientific research. What is changing the public’s view of the drug is the immediate availability of undistorted information; before the web only federal agencies could afford to get information to the masses.

If the concept of prohibition results do not become better understood by the public, the next federal prohibition will be of cigarettes. Use and public acceptance is lower than it’s ever been thanks to education, treatment, advertising regulations, and social sanctions, but some influential people will be impatient and say we can turn our “tobacco free” educational slogans into reality through legislation. If they are successful, they will likely not greatly affect the level of smoking, but cause great overall social harm attempting to do so by force.