The college football season has kicked off, and the NFL’s regular season begins next week, which means sportsbooks are getting ready for the biggest opportunity of the year to sign up new customers and grow the wagering pot. 

Americans are expected to wager a record $30 billion this NFL season through legal gambling, an 8.5% increase from last year, according to estimates by the American Gaming Association.

The biggest players in the space, Flutter-owned FanDuel and DraftKings, are facing growing competition from BetMGM and Caesars. thOer players are looking to get in the game, as online broker Robinhood teamed up with Kalshi to offer football prediction markets.

However, the largest threat these companies face are from the offshore, unlicensed sportsbooks such as Bovada, MyBookie and BetOnline.

It’s something that prosecutors are starting to crack down on.

The Los Angeles city attorney filed a civil enforcement action on Thursday against online sweepstakes casino operator Stake.us and 20 other related companies, including publicly traded Evolution. In the landmark lawsuit, prosecutors allege the companies of running illegal gambling operations and are asking the court to shut down operations and refund player losses.

Earlier this month, 50 attorneys general wrote a letter to the Justice Department asking the federal government to crack down and step up enforcement against unlicensed gambling because states are losing an estimated $4 billion in tax revenue.

Data from geolocation tracking company GeoComply shows states that take active enforcement measures against illegal offshore sportsbooks have a 10% higher growth in active players year over year and had 38% more new player sign-ups in August.