First of all, let's be clear that the "drug debate" is not a moral issue. The selling of drugs is an economic transaction pure and simple, and it is subject to the same laws of supply and demand as any economic transaction is in a free market system. The only reason that people sell drugs is that there are people who want to buy them. Capitalism pure and simple. If there are no buyers, sellers will sell something else that people want to buy, or they will get real jobs in order to make money.
Interdicting the supply of drugs in order to solve the "drug problem" is a fallacy. If you remember from economics class, what happens to the market value of a commodity when its supply shrinks while demand remains constant? Prices increase. Now if the commodity happens to be milk, a large price increase will cause some mild discomfort, but people can easily adjust. They'll either pay more or use less.
Consider the same scenario, but substitute "heroin" for "milk". If we cut the available supply by, say half, prices will skyrocket, just like they will with milk. But unlike people who drink milk, people who use heroin are mostly addicted to it and are not able to adjust to the higher prices by using less-in fact, they must continually increase their dosage as time goes on in order to achieve the same high. So as prices increase addicts will be forced to pay much more for their drug. Since most drug addicts support their habits by stealing, the crime associated with drug use will dramatically increase.
And unlike dairy farmers who sell competing products side-by-side in legally sanctioned supermarkets, heroin suppliers must fight each other for control of the streets in which they sell their products. If the value of the heroin skyrockets, the value of the terrotory controlled by dealers will similarly skyrocket. Street gang violence will markedly increase, since there will be much more economic reason to kill rivals to secure selling territory.
And if we manage to curtail the flow of drugs into the country by an even higher percentage, the above scenario will only get worse. Still higher prices, ever more crime by addicts and ever more violence to control selling territory.
Think the above scenario is just a lot of unproven theory? What I describe actually happened. During prohibition Chicago was the center of the illegal liquor trade in the U.S. The above was played out on the streets, in the alleys and through the bedroom windows of Chicago every single day for over a decade. It only ended when the 18th Amendment was repealed in 1933, makling the selling and consumption of liquor legal again in the U.S.
Prohibition simply doesn't work, as the utter failure of the 18th amendment proves. Our jails are now so overflowing with drug offenders that to make room for them we're forced to release some violent offenders back into society long before they've served-out their sentences We're spending astronomical amounts of money to interdict a tiny percent of the drugs that flow into the country, leaving little money left over to help those who are addicted to break their addiction. This situation has only worsened in the decades since the "war on drugs" became official government policy.
Now let's look at what would happen if drugs were sold legally, in a controlled way (like alcohol, for instance):
1) Governments would tax the sale of drugs and revenues will increase.
2) Supplies and availability of drugs will increase, forcing prices down (basic market economics at work again). Crime committed by addicts will decrease because they won't have to steal as much (or at all) to support their habits.
3) Street dealers will be put out of business, unable to compete with large corporations who can sell drugs for less through legal channels. The violence resulting from drug territory wars will vanish.
4) Since a street gang's power stems from the money it makes selling drugs, gangs will become much less powerful or disappear entirely. (Once liquor prohibition was repealed the crime gangs it spawned quickly vanished.) With the allure of making big bucks selling drugs in a street gang gone, kids will be much less likely to join.
5) Governments will not need to spend huge sums interdicting drug traffic and arresting dealers and addicts. If even a small percentage of this money were to be redirected into treatment programs many more addicts would be able to permanently kick their habits. The net result: addiction rates would likely fall if drugs were legalized.
6) Prisons and jails would have the room necessary to keep offenders that are truly harmful to society locked-up for longer periods.
To reiterate: this isn't a moral issue. People have always used drugs throughout human history, and they always will. This is a fact of human existence, and the utter failure of all past and present "wars on drugs" proves that no amount of government meddling will stop it. The fact that drugs are currently illegal is the root of all of the problems associated with drug use. If you remove the commodity from the black market it becomes just another item sold behind the counter at the drug store or liquor store.
And one more thing: Drug smugglers and drug dealers are the last people who want to see drugs legalized, because they know that their income and power will vanish overnight as soon as the prohibition is lifted.