It Worked Well in the '20s:

WHY A BUNCH OF DEAD MORALISTS WANT TO PREVENT ME FROM SMOKING MARIJUANA

There's no moral high ground to be had in Person A admonishing Person
B about smoking marijuana. It might bother Person A that Person B is
enjoying marijuana somewhere. It may keep Person A up at night, sick
with rage that somewhere, Person B is smoking a joint and listening to
the Beatles. Regardless, Person A has no right whatsoever to prevent
Person B from enjoying marijuana. This is the most fundamental,
vitally important argument to be made in the drug legalization
argument. This is the only one that matters. Sure, there are a host of
other arguments to be made, dealing with everything from the
preposterous hypocrisy of the government to the dubious origins of
drug laws in this country; but this is the most important argument to
be made. Person B's marijuana use does not hurt Person A in any way.
It is, therefore, outside of Person A's authority to prevent Person B
from smoking it. I hope this is clear to everyone.

Marijuana laws began largely as an outgrowth of the "Noble Experiment"
of Prohibition. Whiny moralists feared that, without alcohol, many
would turn to marijuana. Also, in the Southwestern United States,
anti-Mexican sentiment spurred the passage of many of these laws. The
first marijuana legislation in the country, passed by the California
legislature, actually contained racist anti-Mexican propaganda in the
wording of the law.

For some reason, even though we decided that Prohibition was a
terrible idea that didn't work, we're still okay with prohibition
(with a little "p"). Prohibition didn't work because of several
ironclad economic principles. The first is that prohibition of a
mutually beneficial exchange will never work. If tomorrow, the
government made taxis illegal, a black market for taxi services would
spring up overnight.

People, when left alone, will generally choose moral decisions. I can,
and generally do, buy marijuana most everywhere, despite ballooning
government spending to stop me. Yet, I wouldn't have the first idea of
where to go to pay someone to kill someone else. I realize this
happens from time to time, but there isn't a huge black market for it
because most people don't want to kill other people. However, the
criminalization of marijuana produced a huge black market because
people wanted it.

The argument I hear occasionally tossed about is the 'but it is
illegal' argument. This doesn't hold any weight. It is illegal, true,
but the legislature does not have the power to assign morality or
immorality to something. In a perfect world (a world devoid of people
trying to force other people to think like they do, and hence, a world
that can and will not ever exist), the legislature would simply make
illegal all those things that are immoral (immoral in this sense
meaning 'those actions that hurt another person'). Gambling on a
Warriors game and demanding, at gunpoint, that some bank teller empty
the drawer are both illegal. But only one of these actions has any
immorality attached to it. Also, to the proponents of the 'it is
illegal' argument, read the first paragraph.

I saw a commercial once that went something like this: several
twentysomethings were sitting around in different groups, and in each
group one person was saying that they had recently contributed money
to a terrorist organization. The point of this smarmy commercial was
that perhaps your drug money is winding its way to terrorists somewhere.

This may be true. In fact, I'll assume it's true (which is, I imagine,
quite a leap of faith). The person who buys the drugs and whose money
goes to support the terrorists is much less complicit, if at all, than
the person who forced him to take that route to obtain his drugs. This
person would, most likely, much rather buy his drugs from a Long's
Drugs than he would some guy on the street. Unfortunately, this isn't
open to him, so he does the best he can. No, this
"drug-money-to-the-terrorists"
model of the market has been imposed on the drug trade by the very
same moralists who made it illegal in the first place. Indeed the very
act of making drugs illegal forced the markets to operate in this way.

If the terrorists are getting all of this money from my buying
marijuana, and the government has such a problem with this, then
perhaps the same government could allow me to buy marijuana from the
store, and thus from a completely transparent and traceable market. I
don't worry that the money I spend on a Pepsi is going to terrorists
because the entire market, from the factory that makes the plastic
bottles to the Pepsi bottling plant and all the way to my living room
where I consume it, is completely transparent and subject to the laws
of both this country and the world at large.

It's only when you create a black market that you have to worry about
where your money is going. And, hey, I didn't create the black market.
I've simply been forced to turn to it for all of my drug needs.