The PokerStars website is available in the United States, but only players in a handful of states can access the real money games listed there. This isn't because PokerStars doesn't want you at the tables. The poker site is active in almost all the US states that have legalized online poker.
You are in an existing poker cash game or have an active Casino session. You are under 19. You must be at least 19 years old to play on PokerStars in Ontario. You can't legally gamble if you're under this age and will need to withdraw your funds from your account balance.
