I am very much your ideological opponent on this issue, but I agree that there is a solid ethical case for obeying the law regardless of its content, because the rule of law is a phenomenal human achievement that enables us to live vastly more peaceful existences than would be possible if it were absent. My own lifestyle, which doesn't involve much concern at all for self-defense or alliance building wouldn't be possible in conditions with significantly weaker rule of law, and the rule of law is not a given — it can be threatened; we could lose it.
But there's another consideration that's in tension with that one. No one ever ascented to the laws that they're governed by. Yes, there are endless backs and forth in the philosophical literature on this point, but I think the strongest case that governments can justly impose restrictions without explicit consent is going to have to say that there are some kinds of restrictions that governments can impose, but some that they can't. Otherwise you're committed to saying that governments can justly enforce regimes of slavery and so on. The question is how much less evil than slavery do you have to get before governments can justly impose restrictions on their subjects.
You say that selling drugs is not value neutral. I agree. It's value-positive. Drug dealers are heroes: they put their lives and freedoms on the line to let others enjoy the cognitive liberty that their governments would deprive them of. The idea of cognitive liberty is that it is a human right to have the freedom to shape your conscious experience as you see fit. It's not presently recognized as a human right by any nation, but neither was freedom of thought some centuries ago, yet we don't recognize historical rulers as particularly respectful of human rights. The legal scholar Richard Glen Boire has spent his career elaborating and promoting this principle.
You're, I take it, concerned that drugs cause harm to the people who use them and the people near those who use them. Drugs definitely do have the potential to cause harm (although cannabis, the drug in question, is especially weak in its potential to cause harm). But the idea that people have about the harm of drugs is distorted in three main ways:
1. Prohibition makes drugs far more expensive than they would be without distortionary market policy. Much of the harm of drugs comes from people being driven into poverty by addiction. This is almost entirely a consequence of prohibition, and would be a much lesser problem under a regime that respected cognitive liberty.
2. There's selection bias in the stories that we hear about users of drugs. Due to the stigma and legal risks around drug use, people who are able to keep their drug use private choose to keep it private, and we get an exaggerated sample of people who end up in need of an intervention or on the streets as a result of their drug use. See the recent book Drug Use For Grown-Ups by Dr. Carl Hart for more on this.
3. The lack of drug education, and the belief — widespread even among users of drugs — that drug use is inherently self destructive, leads people to be far more reckless in their drug use than is necessary. Certainly there will always be people who are reckless with drugs, but we can do a lot better than having young people learn about drugs from their peers in contexts where it's uncool to be concerned with safety, and half the point of the activity is to signal disregard for authority and rules.
I'm not sure that respecting people's cognitive liberty wouldn't result in more people suffering at the hands of their own drug use, but I suspect that it would be fewer than most people imagine. And cognitive liberty is something that's valuable in itself.