A quick breakdown:

Drug legalisiation does not increase usage

When Portugal decriminalised drug usage 10 years ago many worried drug usage would rise, it hasn’t. In fact it has fallen by 50%. People take drugs regardless of legality or illegality, but many also take them because it is cool and rebellious, making it legal removes this incentive to take drugs.

http://blogs.independent.co.uk/2012/02/02/the-case-for-the-legalisation-of-drugs/

http://www.forbes.com/sites/erikkain/2011/07/05/ten-years-after-decriminalization-drug-abuse-down-by-half-in-portugal/

Other sources also seem to indicated that drug legalisation doesn’t increase usage

http://www.rawstory.com/rs/2012/07/07/global-report-decriminalization-does-not-increase-rates-of-drug-use/

http://druglibrary.net/schaffer/activist/claim3.htm

Drugs are less harmful than many other legal substances

Alcohol is more dangerous than heroin, crack or ecstasy according to Professor David Nutt, a leading drug expert

http://www.dailymail.co.uk/health/article-1325472/Professor-David-Nutt-Alcohol-harmful-heroin-crack-Ecstasy.html

According to the Governments own advisory panel on drugs, ecstacy is less harmful than riding a horse

http://www.telegraph.co.uk/news/uknews/law-and-order/4537874/Ecstasy-no-more-dangerous-than-horse-riding.html

It is frankly hypocritical to say drugs should be illegal as they are dangerous yet things that are more dangerous like alcohol, smoking, or skydiving should be legal.

It should also be up to an individual as to what they decide to do with their body.

Making drugs illegal makes them more dangerous

When you buy a product from a shop it may come with a warranty, if you buy food and it turns out to be gone off you can take it back and complain. With drugs you can’t, there are no stamps of approval, you do not know what has gone into it. Unscrupulous dealers mix the drugs they have with many other things to stretch out the supplies they have and make more profit. If drugs were legal those that tried to do this would go out of business or be arrested, as it is if you take drugs currently you are at risk of getting something even worse.

Making drugs illegal helps organised crime

When legitimate business can’t sell something who does? The answer is of course criminals. Just like alcohol prohibition enriched mob bosses such as Al Capone, drug prohibition means that organised crime groups can easily earn money by dealing drugs. If drugs were legal a huge black market would be wiped off instantly.

http://news.bbc.co.uk/1/hi/8319249.stm

http://abcnews.go.com/Blotter/selling-drugs-fund-terror-al-qaeda-linked-cocaine/story?id=9373341#.UIK3XWfWqSo

http://www.unodc.org/unodc/en/frontpage/drug-trafficking-and-the-financing-of-terrorism.html

Police spend millions of pounds and 20% of their time on chasing drugs and drug dealers instead of dealing with serious crimes

http://blogs.independent.co.uk/2012/02/02/the-case-for-the-legalisation-of-drugs/

20% of police time is spent on drugs, imagine how many more murders, rapes, burglaries and other crimes the police could deal with if they didn’t have to spend (waste) so much time and money tracking down drug users and dealers