The Province – A businessman who lost $500,000 on table games at a Las Vegas casino on Super Bowl weekend is arguing that he shouldn’t have to pay because he was blackout drunk. Southern California gambler Mark Johnston, 52, is suing the Downtown Grand for loaning him money and serving him drinks when he was visibly intoxicated. Nevada law bars casinos from allowing obviously drunk patrons to gamble and from serving them comped drinks. Johnston’s attorney, Sean Lyttle, says the Grand, which opened last November in the old part of Las Vegas, intends to pursue Johnston for trying to shirk…