I don’t think that is what the posted is advocating. He is discussing whether drug use itself while absolutely being immoral should also be a punishable criminal offense. Not everything that is immoral is also illegal, for example adultery is much more condemned in the Bible than any type of drug use, yet you can go to prison for using drugs and there is no legal penalty for adultery. My personal belief is that no, private immorality should not be a punishable offense. While definitely immoral, the war on drugs has done absolutely nothing to reduce drug use and has cost this country an absolute fortune. I have seen how drug use destroys people first hand, and while I would never advocate anyone ever using drugs, it seems that the penalty that we apply to those who use drugs (prison, felony convictions) is just, if not more damaging than the actual drug use itself.
As far as official Catholic Doctrine goes, I am not aware of anything in it that requires you to be for or against any Civil laws affecting other people. For example, we can be pro-life, but are not required by our faith to vote for a pro-life candidate. I think, but again I am not positive, but you are only responsible for your own morality and can not contribute to the immorality of others, but this does not apply to things being legal or illegal.