Conservative? I don't think so.
There is no one anymore "conservative" than William F. Buckley, founder of The National Review magazine which was the founding of the modern American conservative movement, and he long advocated decriminalizing marijuana - not making it free and legal, just not creating an economy for the gangsters out of it and putting people in long-term incarceration for possessing more than an ounce.
His view, that we have created the crime environment, and it is winning, just as it won with prohibition.
This nation had the worst heroin and opium epidemic of its history, from the late 1800s to the early 1900s. It was fought, and quit successfully with large and consistent amounts of public education, in schools and the media and treatment in publicly supported clinics. We did not create a socially destructive criminal environment for it. It had been reduced to a minor social nuisance when we started enacting drug control laws in the 1920s.
Just imagine how many criminals there would be if tobacco was illegal, and how criminally profitable it would be.
We would be better off literally buying the entire drug supply in Columbia and Afghanistan - 100% of it, at prices the drug cartels could not afford. No supply, no crime. Then we'd just have to help the current addicts through their withdrawal.
Oh, I forgot, other drugs are being invented all the time.
Can't win. Just help the addicts try to get off and don't make a criminal mess out of whatever you do to suppress the use of bad substances. The crime environment you create is worse than the numbers of people who will not avoid the addictions. Those numbers are probably the same no matter what.
Conservative? I don't think so.