From the LVRJ:
"Since offering daily fantasy sports in Nevada is illegal without the proper license, all unlicensed activities must ceases and desist from the date of this notice," wrote Gaming Control Board Chairman A.G. Burnett.
Burnett said Nevada sports book operators could offer daily fantasy sports, however, they "should exercise discretion in participating in business associations with daily fantasy sports operators that have not obtained Nevada gaming approvals."
Added Burnett in an interview, "We're not saying they can't do (daily fantasy sports). We're saying they can do this as long as they have a gaming license."
The Control Board, through an "exhaustive analysis" by the Nevada Attorney General's office, determined daily fantasy sports constitutes sports wagering. http://www.reviewjournal.com/business/casinos-gaming/nevada-gaming-regulators-ban-daily-fantasy-sports-the-state
Fan Duel has been around since 2009 and Nevada could not care less about it until now, when they have become a billion dollar industry and probably has taken a significant amount of money from the casinos in Nevada.
And this is what the gaming regulators do in Nevada, protect the casinos.
Next thing they will ban is playing the stock market.