Well, Mr. Dearden is correct that there is nothing in the WTO rules or dealing with the WTO that regulates the quality, safety, and efficacy of drugs. From that standpoint, there's no liability.
Secondly, as a general proposition, virtually all countries maintain domestic regulatory authorities that are responsible for determining the quality and approving the drugs that are put on their domestic markets. But in this case there is an even more practical issue and solution to what you're mentioning.
Virtually all of the antiretroviral drugs being supplied in large quantities into Africa are being supplied under the terms of large-scale procurement funding that is coming from multilateral organizations and donor funds like the global fund. All of those funds require that the drugs that are being purchased meet strict compliance guidelines. Those strict compliance guidelines may often be and are typically the WHO pre-qualification program.
As a practical matter, the notion that Canada would be exporting unqualified or unsafe drugs under this system is very unlikely, and I would just end with that.