Sorry, but there is no such law. There's a minor league baseball team (AAA) and there have been other professional teams in Las Vegas over the years, although none from the four major professional leagues. I remember when Las Vegas had a CFL team. Biggest obstacle to landing one from the big four is the lack of a suitable, modern facility with the luxury suites, club level seats, etc. Something the new arena will have. There will always be some perception of possible impropriety which could keep the major leagues away. The NFL in particular likes to distance itself from Las Vegas while hypocritically doing everything in its power to facilitate 'fantasy football'. But there are no laws prohibiting professional sports teams in Nevada.