Of course there would be. But those negative effects are outweighed by the even more negative effects of Federal prohibition. That was Buckley's point.
Lots of people have misunderstood the nature of the post I wrote asking the question you quoted. You are one of those people.
I was NOT arguing that drugs should only be legalized if there were no negative effects in doing so. I was simply trying to solicit the poster’s views on what those negative effects would be without me “leading the witness,” so to speak.