Let me explain what I mean. There are just laws, and there are unjust laws. Just laws should be obeyed. Unjust laws should be changed. If you think a given law is unjust, you should be campaigning to change it, not breaking it willy-nilly. The cost of people taking illegal drugs is huge, from the drain on police and prison resources to the creation of the organized crime rings which support the drug industry, and if you're taking illegal drugs you're responsible for all of that. If you are correct and drug laws are unjust then... well shit, changing them is an important task for you, and you should get cracking on that.
Right now there's no great consensus over whether drug laws are just or unjust, but the majority wants to keep drugs illegal, even in California which recently failed to pass (by a huge majority) a legalization of marijuana. If you choose to live in a democratic society, why not obey the democratically ordained laws?
Yes, there are circumstances when it is acceptable to break a law which you regard as unjust. One such circumstance is civil disobedience, where you break an unjust law with the intention of getting caught and punished so that you can bring attention to how unjust that law is, but if you're not (courageously) trying to get caught and punished you're not a civil disobedient. Another such circumstance is if the law is so horrendously unjust that following it will directly harm others, but that certainly doesn't apply in this case.
In conclusion, if you want to take drugs then campaign for drug legalization. But don't go round breaking the democratically-devised law in the meantime.