It's your god-given right to put whatever you want in your body HOWEVER it is subject to what kind of effect you will have on other people while you live near them. For example streets full of junkies does not inspire confidence.
You are a free man up to a point....
And that point is if your behaviour can spill over and harm other people in society. For example lets look at a small tribe of people in the jungle. They have laws too. Laws are required when humans share territory.
Animal kingdom? yes they have laws as well - and laws that change over time based on territory, behaviour, survival of the species and so on. Ours just happen to be written down and discussed
In the case of weed, I think it should be fully legal and available for purchase over the counter just like alcohol or cigarettes. I think that they should have testing kits for work and for drivers to ensure that smoking is restricted to the home. In fact, smoking in general should not be allowed in public except for parks or designated areas.
We don't have to force our love of pot on other people. We need to be smart about it. Prove we're smart - and people will calm down about weed murdering babies or whatever.
I'm a fairly smart person - I program games for a living, and I'm a complete and utter pot head. I love my weed, but I wouldn't dream of exposing other people, much less families and children to the harsh smell of skunk