Marijuana should be regulated by the government because of the control that they would inevitably have over the marijuana sector of drug use. Currently, states that have penalties, fines, and jail time for marijuana use/possession create a larger black market for the drug in question. Regulations established by the government could explicitly make it known who is producing the marijuana, who has the ability to legally distribute, who can smoke legally, etc. Furthermore, the medical benefits of marijuana seem to be advancing (with discoveries such as marijuana being an aid for AIDs patients, glaucoma, etc.; Check out the marijuana strain Charlotte's Web). If it wasn't for a market where marijuana use was legalized, such advancements for the drug would have never found their way to patients such as Charlotte Figi, who suffered from severe seizures every week.
I agree with the fact that it should be regulated. However the problem with certain states legalizing it is that it causes a media uproar. The minute there is a state that approves of marijuana their is going to be a amount of people that are going to want to go to that state to part take in the movement. The problem with that is that there are still going to be specific parts in the law that people don't realize. In the case of Colorado it is legal, however it is still illegal to smoke it outside, as well as selling it to a certain amount. Now I'm not saying that its a bad idea to to legalize it and I am not against the effects that it has of special patients. However I am against the fact that it is easy for one to get medical marijuana. Having known plenty of people that use marijuana recreational, by seeing their experience in being able to get their hands on medical marijuana without having a prescription goes against the idea of giving a prescription out.