I've written before about the Cons' blatant strategy of saying just enough about regulating greenhouse gas emissions from the oil industry to confuse voters about the issue while blocking the way toward any action. And so the real news in their offer to let the U.S. write the regulations they've been promising "next year" for seven years and counting is the prospect that it might actually result in some policy coming into effect.
That is, assuming one thinks the same prime minister who's gleefully played Lucy-with-the-football with the Canadian public on this exact issue will voluntarily follow through after the Obama administration provides any go-ahead to TransCanada. And it's especially noteworthy that the only force which seems capable of motivating Harper to even feign interest in climate change is a profit opportunity for a pipeline operator - signalling that the now more than ever, the Cons are transparently placing the interests of the oil sector above those of the general public.
All of which is to say that Obama should be careful to get the exact details of any "joint action" in writing and in law before even hinting at approving KXL - because there isn't much evidence the Cons are otherwise about to deviate from their track record of breaking every promise they make on climate change.
(The Mound of Sound and BigCityLib have more.)