The word "drugs" has various shades of meanings.
1. From a technical, scientific view, it includes drugs bought with a doctor's prescription such as Asthma medication, as well as drugs which are currently illegal such as methamphetamine.
2. From an ordinary person point of view (which is scientifically inaccurate), the term "drugs" excludes legitimate drugs and includes only those illegal drugs mentioned earlier.
I'll address my viewpoints with respect to both kinds of meanings.
Drugs bought with a doctor's prescription should be legal to possess because there are people who genuinely need to be treated for whatever medical issue they have. However, drugs which are currently illegal such as methamphetamine should never become legal, for several reasons. First, since those drugs are usually addictive, its legalisation can (but not necessarily) encourage more people to try them out, leading over time to social decay. Second, it's not an issue of human rights or valuing freedom, because drugs have effects on the mind, and those affects have been clearly demonstrated to control behaviour, especially leading to violent behaviour and serious withdrawal symptoms involving violence as well. Third, as a country in the 21st century we should strive for the betterment of the human race, rather than cling to ideas of freedom at the expense of lowering human health.
Having said that, there are good arguments for the legalisation of drugs which are already illegal. These counter-arguments ought to be recognised if we are to have a serious discussion regarding legalisation. As you all know there are many (but not all) incidents where police officers have planted drugs to win convictions. Obviously this is a problem and there is not much that can be done to overcome it. Once the prosecution proves that you were in possession of the drugs, whether you had knowledge or not, it is very difficult to rebut that presumption in court. Legalisation seems like the only answer to overcome such a problem. There are also rational mind theories which suggest that legalisation will not encourage many people to take up drugs. The theory says that taking illegal drugs are irrational, so it won't matter if it's legal or not.
That's my view on drugs.
Of course, the debate is not that clear cut. There are good arguments for either side and I feel a genuine person can hold either view. My view is more for currently illegal drugs to remain illegal, and for people to be able to purchase drugs at a chemist with a doctor's prescription.