Marijuana is now legal in some U.S. states but the issue of enforcing pot-DUI cases is proving a legal minefield. Recently the Wall Street Journal reported on how lawmakers are “struggling to create rules” for how to identify drivers who are under the influence of pot. It seems identifying pot impairment is not as easy or straightforward as testing for alcohol. “There is no broad agreement over what blood level of THC – marijuana’s psychoactive ingredient – impairs driving,” stated the Wall St...