So the House passes a bill requiring Canada to meet the unmeetable Kyoto targets. The Environment Minister initially says the government will just ignore the law (which would be totally unconstitutional, needless to say). Harper now has some gobbledygook about how he will -- on the one hand -- respect it, but -- on the other hand -- it doesn't mean anything.
The Government has an alternative. It can instruct the Governor General not to give royal assent to the bill in the event it passes the Senate. It's been done.
Of course, it would make a perfectly legitimate confidence issue if the opposition parties want to go that way.
Update: Matthew Shugart has a good post on the constitutional position.