tedster - 11:07 pm on Sep 15, 2011 (gmt 0)

But where would the url be sourced from? You don't want a canonical link to be generated on the fly - it should be actually written into the page.

If you're concerned about stripping any bad query strings, I'd do that in your own .htaccess file, not with the canonical link tag that depends on the search engines getting it right.