Now that the two largest online daily fantasy sports sites are back in the news—nearing a deal to merge into a company drawing $100 million in revenue, according to the Wall Street Journal—it’s a good time to answer a nasty, nagging question: Are these sites legal? Because the companies in question, FanDuel and DraftKings, are backed, respectively, by fat investments from Comcast and 21st Century Fox, it’s apparent that some high-powered attorneys must think that they are. And in fact, at this point, they’re clearly legal in at least nine states. So the real question is whether they will become...