Monetary policy is focused on returning inflation to target over the medium term, and the value of the dollar is determined in markets. I think the focus on inflation is the best contribution that Canadian monetary policy can make to the economic and financial welfare of Canada, because ultimately, attempting to lean against movements in the dollar would force adjustment onto economic activity, employment, prices, and wages within the economy, and in that way would create additional volatility but also undo any or at least some of the impact of leaning against movements in the dollar.
On March 12th, 2015. See this statement in context.