I dont know this Sérgio Sousa, but he is my friends' friend, so I will try to be polite. He says criminalization led to better quality drugs due to more organized supply (see his post here). And lower prices!
EVERY THING ELSE CONSTANT, Criminalization increases prices because it ADVERSELY affects supply (since non-criminals won't supply) and increases prices further still because you have to compensate the entrepreneur for the high risk incurred. Sérgio talks about high profits in illegal markets. MAN YOU HAVE TO CONTROL FOR RISK.
And Sérgio does not mention the most important thing: NEGATIVE EXTERNALITIES. Criminalization generates violence, which spills over. Why beer producers wear suits and cocaine producers carry weapons? Because of stupid criminalization! In the 20s, in USA, beer producers carried guns too.
How to account for the lower prices then? A much more plausible explanation is that law enforcement turned laxer, increasing supply.