The legalization of marijuana is an ongoing battle that was been thwarted more times than it has been won. In the United States, was at one time legal. Starting in 1906 marijuana was considered a poison and banning of marijuana occurred during the 1920s. By the 1930s, every state regulated marijuana with the Uniform State Narcotic Drug Act and the eventual Marijuana Tax Act of 1937 which allowed for it to be used for medical and industrial use with a tax paid. In 1970, the Controlled Substances Act of 1970 saw marijuana classified as a schedule I drug meaning it had a high chance of abuse and no medical use.
Several acts have been passed to halt the legalization of marijuana in the U.S and can be said that facts have been skewed in favor of keeping marijuana largely illegal.
There are a number of reasons for the illegal status of marijuana in the U.S. Politics is one such reason, but there are a number branching reasons related to politics. Hemp had an industrial use that would make it cheaper and more readily available than wood. This would mean that trees wouldn’t need to be cut down for manufacturing purposes given that trees can take many, many years to grow and that a lack of trees would bring about great environmental concerns in regards to displacing wildlife and the atmosphere. In short, hemp—particularly cannabis sativa—could’ve taken the pressure off of trees as far as slashing and burning is concerned.
So far that would seem more industrial than political, but why not keep marijuana legal for widespread industrial use if not for politics. The element of politics comes into play when someone has an interest—something to gain and something to lose if hemp was to replace wood when it comes to manufacturing certain products. This was the case in the mid-1930s as a the William Randolph Hearst (who had interests in wood and ran a media empire), Andrew Mellon, and the Du Pont family (who held interests in nylon which came out of their labs) initiated an attempt to kill the growing hemp industry even with academic papers by USDA scientists showing the effectiveness of hemp hurds over pulp.
Another reason for its illegal nature is skewing of information to paint it unfavorably. Experiments and studies have shown than marijuana is far less dangerous and less damaging to the body than cigarettes and alcohol—both of which are legal, sold in stores, promoted openly in commercials, and so on. In addition to cannabis sativa having an industrial use, it has a medical use which has been promoted heavily in attempts to get it legalized. Hearst—who had a newspaper empire at the time—used his media vehicle to demonize marijuana.
In the U.S marijuana is legal in some capacity in certain states and cities. While a federal-level re-regulation of marijuana would be required to give it a legal status to where it could be sold in stores, it has been made legal in places such as Washington State and Colorado and for medical use elsewhere.