Let's see if I can follow the logic.
Guns are used to do bad things. We should enact very strict gun laws to prevent people from getting and using guns.
Drugs are used to do bad things. We enacted laws to restrict drug sales, but they have done little to prevent people from getting and using drugs.
Of course, the converse is true, too.
My point with all this is that the problem may not be gun laws, or drug laws, or anything so mundane. Perhaps people who want to do these things simply don't care? If I want to kill someone, I'll get a gun. If I have to buy it illegally, or can go to Wal-Mart . . . I'm going to get one.
Same with drugs. Just because coke isn't legal, it doesn't seem to stop millions (thousands, I don't know or care) from getting it whenever they want.