This is a bit of a grey area. In 2006, the Unlawful Internet Gambling Enforcement Act (UIGEA) banned online gambling in the USA. However, the law was worded in such a way that players could not face any legal consequences for gambling online. So, many operators moved offshore to other jurisdictions and continued to serve American players. It’s not illegal for you to play, but the operators are technically operating outside the strict confines of the law.