Just simply, since the Uruguay Round, Canada has taken one article 28 action, with respect to the major rewriting of the Canadian customs tariff in 1998. In collapsing some tariff items, there were some minor areas where tariffs were raised minimally, affecting minimal amounts of trade. Overall, though, there was a net $90 million reduction in duties collected, so it was of broad benefit to all members of the WTO. So it's similar, and in fact a technical measure, as Graham pointed out, like the enlarging of the European Union.
On June 1st, 2006. See this statement in context.