Right, I'll expand on what I said in the Matt Stevens topic, and I'm only taliking about mainstream drugs:
1. The effects of a drug, on their own, do no harm to anyone but the user.
2. As a reply to point 1, I'm sure that people will bring up the quite valid argument of cocaine users and drinkers being lary. And believe me, I know all about it. But currently, cocaine is illegal, expensive, and consumed in a disgusting manner (I don't fancy snorting anything up my nose); yet the market for it is huge in spite of all this. We must accept that, whatever the authorities try, substances are always available to those who want them.
Drugs are like prostitution. There will always be demand, and thus there will always be supply. But the worst exploitations are committed when suppliers attempt to meet the demand for something illegal. I'll use prostitution as an example: If we accept that there will always be demand, then there will always be prostitutes. However, if it is illegal then these prostitutes get no rights. They have no protection from their services being abused; no chance of unionisation; thus no safety net that everyone else in employment expects. I needn't go in to details about the exploitation of prostitutes by pimps and suchlike.
Now I'll put this example onto drugs:
Ecstasy: MDMA pills were introduced in the USA about 30 years ago by, of all people, a priest in Texas. He used to give them to people for free because of the overwhelming euphoria they encouraged. After gaining popularity in the 80s, and having no serious health/ addiction risks attatched to them, they were made illegal by Reagan's government as part of a broad anti-drugs campaign, and the rest of the world followed suit. The science behind their illegality was based on a study saying that pills fried your brain; this study has not only been disproved subsequently; but the scientists who conducted it actually did the tests on another substance alltogether. Anyway, the result is that Ecstasy is now a Class A drug in Britain, with little to no solid evidence that it causes either long-term health damage, or that it causes anti-social behaviour. The major risk to do with Ecstasy itself is impurity. Why are there impurities? Because profit driven criminals with no moral scruples about the wellbeing of their customers dilute pills in order to get more pills from the same amount of MDMA. Were these pills legal, and regulated in the same way prescription drugs are regulated, this would not be an issue.
Cocaine & Heroin: Coca plants are grown by incredibly poor farmers in Peruvian and Colombian jungles. These farmers must provide a living for their family, which they cannot do by any other means. They are coerced into coca farming by local gangs; for them it is the only alternative to living subsistently. The coca leaves are then taken to be processed, a process that still takes place in the open air, in the jungle, and is still carried out by the poor. Heroin, as you know, is produced by incredibly poor people in Afghanistan, who are also exploited by gangs.
The transportation and smuggling process then begins... and this inevitably causes trouble and strife. It's not uncommon for cocaine to be smuggled inside a human body; usually a carrier who has been forced into it.
Were these drugs legal, they could be imported like anything else, grown as crops like anything else, and hence the exploitation and violence would be removed from the process. This works as well for Cannabis grown abroad.
3. Surely drug addicts commit a lot of felonies to feed their addiction? Yes, they do. But, if it was legal? Well, I'm not saying it should be sold at every off-licence. Here's where tobacco and alcohol come in. These are both addictive and dangerous drugs. But they coexist with society largely because they are extremely well regulated. Heroin, cocaine, etc. would have to be sold from pharmacies. But being sold over the counter means that the government has the ability to regulate the price. Which ought to see the price drop hugely. Lower price = less crime.
4. Most gang crime os over drugs. If drugs are legalised, then your street dealer is neutered. He's got no reason to stand outside all day on a corner. Which means good areas for selling will not be coveted by others. Which means killings, and other forms of violence will not take place. In the UK especially, street gangs these days are small-time drug crews. They're not into protection racketeering or anything like that. So there's really no need for a turf war if there's no profit to be made from the turf.
5. Hallucinogens are the only area I haven't covered. LSD, Mushrooms, Ketamine. Well, these are not addictive and do not have a detrimental effect on society like heroin does. Their effect is purely on the person using them. Which means it's personal choice.
I'll just finish up with this: Drug users themselves are not the problem. The biggest potential problems with the drugs trade come with the sort of men in charge of supply. Criminalising it means the men in charge will be criminals. Legalising it means they will be businessmen.[/b]