Here's the gist of it.
For the most part, President Perez's suggestion has been warmly received throughout the region, earning praise from both the left and the right for calling for an approach based upon decriminalisation. While I am sympathetic, I am afraid that President Perez's suggestion might have set back efforts to achieve a smarter regional drug policy. Perez must have known that the United States would come out forcefully against his suggestion to legalise the production, transportation, and consumption of all drugs.
Had Perez suggested that the region discuss decriminalising only marijuana, it would have been more difficult for the US to have fought back as forcefully against the notion. There have already been efforts in the United States, Mexico, Argentina, and other countries to decriminalise small amounts of marijuana. There does not appear to be much of an appetite to extend the same reform to cocaine or other drugs, as was shown by the US's response to Bolivian President Evo Morales's "coca, not cocaine", policy. While still a long shot, a policy change targeted at marijuana would have been a much more viable goal than a reform involving all illegal drugs.
Perez also did not take into consideration that the United States is in the midst of a presidential campaign where taking a tough stand against external threats, wisely or not, is expected. As University of Miami professor Bruce Bagley said, "The last thing Obama wants is a decriminalisation debate in the midst of this campaign". Remember, Perez did not bring up decriminalisation during his campaign for the presidency. It was only after he was elected that he found it opportune to introduce the policy. He should not have expected President Obama and his administration to have responded any differently. I understand that Perez and the other presidents want change now, but they might have just made it more difficult for President Obama to make any reforms.