Not only that, but we need more accurate testing, so in the event someone is hurt while on, say, a construction job, they can test him to see if he was high *while on the job* instead of a highly inaccurate THC test that just gives you a yes or no to of the person smoked weed within the last few weeks.
That way you can say "you're allowed to smoke pot off the clock, but if you're high at work and your job is dangerous we will fire you" which I think is more than fair.