How is this site legal? (mysterybrand.net)

How is a site like this legal? The U.S. has strict guidelines for online gambling, yet these sites pop up and scam many people (They say you can win a $250 million dollar mansion that is actually listed on Zillow).

H3H3 made a video calling out the site and its promoters, you can watch it here: https://www.youtube.com/watch?v=3ewyEF3Wd9M.