Nick Diaz himself said that he can't guarantee he'll pass the urine test. The last time he tested positive for inactive THC metabolites, the AC was very skeptical of Diaz's claim that he hadn't used marijuana for weeks before UFC 143. Wouldn't it have been great if Diaz had had rock-solid evidence that he doesn't compete under the influence?
Diaz should take an extra blood test for active THC metabolites after UFC 158 so that, if he fails the urine test for inactive metabolites, he'll be armed with this evidence. It would be interesting--both politically and legally--to have a commission rule the bout a no-contest if Diaz holds irrefutable proof that he wasn't endangering himself or GSP by fighting high.
Anyway, I realize there isn't much time before the fight and this campaign is pretty futile. If you feel like it, though, join me by tweeting this idea to @CesarGracieBJJ, @NickDiaz209, and whoever else; I used the hashtag #DiazBloodTest