Anti-drug position: The government should outlaw certain drugs, because people often behave irresponsibly or even dangerously when they consume them, and some of those drugs can also be dangerous to one's health. Legalized drugs would impose a burden on society, the safety of our roads, the health care system, etc.
Pro-freedom position: It is a violation of a person's natural rights for the government to imprison or harm him merely for possessing, selling, or consuming a drug. A person owns his own body, and therefore any decision that only affects his body and nobody else's is purely his own. If he has violated someone's natural rights (life, liberty, or private property), whether influenced by drugs or not, then of course a crime has been committed and should be dealt with accordingly. But buying, selling, possessing, or consuming a drug in the absence of a violation of anyone's natural rights is not a crime.
A couple of obvious questions present themselves: If, say, marijuana is illegal ostensibly because it alters a person's judgment, why is alcohol legal? Alcohol certainly alters a person's judgment. Furthermore, whereas people under the influence of alcohol tend to become more aggressive and often even belligerent, people under the influence of marijuana tend to become less aggressive and more relaxed. Similarly, if some drugs are illegal ostensibly because of their negative health effects, why is tobacco legal? Tobacco, whether smoked or chewed, is strongly correlated with cancer.
I assert that existing drug laws are logically inconsistent. Logical consistency ultimately requires one of two alternatives: (a) prohibit all drugs, or (b) legalize all drugs.
Prohibiting all drugs is not possible due to the inherently arbitrary definition of the word "drug." If one defines a drug as a substance that has an effect on one's body and/or mind, then every atom, molecule, compound, or mixture in existence would have to be defined as a drug: If one were to ingest, smoke, or handle enough of anything, it would have a noticeable effect on one's body and/or mind. Some substances just happen to have more of an effect than others. The only non-arbitrary, logically consistent alternative is to legalize all drugs.
A lot of people would probably be surprised to learn that one of the most profound discoveries in the biological sciences in the history of the human race was made by a man while he was tripping on acid. Graham Hancock explains in his 2007 book Supernatural:
In late July 2004, the Nobel Prize-winning biologist Francis Crick, co-discoverer of the structure of DNA, died at the age of 88, and soon afterwards a little-known fact of his life hit the tabloid press. This was that when he was working at the Cavendish Laboratory in Cambridge in the early 1950s, he frequently used LSD (which remained legal until the mid-1960s) as a "thinking tool" to boost his mental powers. According to a report published in London on August 8, 2004 in The Mail on Sunday, Crick had privately admitted to colleagues that he was under the influence of LSD in 1953 at the moment when he "perceived the double helix shape" and unraveled the structure of DNA.
You can read the cited article here.
The fact that Crick discovered the famous double helix shape of DNA while under the influence of LSD doesn't necessarily mean that he would never have discovered it without LSD. Even if he hadn't, perhaps somebody else would have made the discovery without LSD. Independent, near-simultaneous discoveries are common throughout the history of science. Nevertheless, Crick's acid-trip discovery should at least make us pause and consider the possibility that maybe -- just maybe -- some drugs that are currently illegal can, are, and have been, used responsibly as tools for various purposes.
For ages, shamans in countless hunter-gatherer societies throughout the world have used the substances found in various psychoactive plants as the foundation of their religions. These people have claimed, and still claim, that the psychedelic substances -- ayahuasca, psilocybin mushrooms, ibogaine, mescaline, etc. -- open a gate to the "spirit world" that allows them to enter and explore. Maybe it's true, and maybe it's not. I suppose one actually must take a given drug and experience the result firsthand before one knows for sure.
Have government officials experienced each and every psychedelic substance that they have banned virtually worldwide? Of course not. Even if they had, what right does a government have to tell people which inner experiences they are and are not allowed to have?
For those who would argue that prohibiting drugs isn't primarily about banning certain inner experiences, but rather preventing people from harming themselves or others, I ask this: If that is the case, then why should people be allowed to drink alcohol? Or own knives and guns? Or drive cars?
Are we adults, or are we children? The War on Drugs is a war on natural rights. It is a war on freedom and personal responsibility.