I have read that literature and I have also spent a lot of time in Portugal. Actually, I was just talking to the director of that program a week ago.
Portugal is going through a hard time right now. Overdoses are at about a 12-year high. At least early on, the program did seem to have some benefits from the great expansion of services around addiction. The HIV rate among people who used drugs dropped, and that was certainly very positive.
Portugal also has dissuasion committees, which are able to put some pressure on people who have problematic drug problems to change their behaviour. That is something that was often forgotten when people talked about the Portugal model. They think it's libertarian, and everyone does whatever they want. That is really not the case.
A big difference that goes beyond policy is that the cultures are very different. Portugal is different from both the U.S. and Canada in that it is a country that has a very strong Catholic history, a very communitarian society and a lot of social control on behaviour. When it backed off from the legal control, there was still tremendous social control from families and communities. There was disapproval of drug use, which is particularly less common in the western U.S. and western Canada.
Places that have tried to copy that approach—for example, the city near where I live, which is San Francisco—as well as the cities of Portland, Seattle, and Vancouver haven't had the same results as Portugal. With the same policies and different cultures, you get different results.