Players will be blocked on Oct. 13, with balances still available for withdrawal and no timetable for a licensed return.
Eligible players can unlock up to $250 in rewards through Oct. 16 and play for a 70-place prize pool on Oct. 18.
The appeal tests whether Ontario can manage its side of online poker and other peer-to-peer games involving foreign players.
Casino revenue rose 25.4% from a year earlier, while sports betting and peer-to-peer poker both recorded annual declines.
The province will argue for international player sharing in a dispute that could reshape regulated online poker in Canada.
Sports wagers reached C$1.03 billion in June, while active accounts rose to 1.319 million and casino revenue eased from a record May.
Ring-fenced play and thin liquidity have left the vertical without a launch, even as the province’s new iGaming market expands.
The province’s new regulated market opens with ring-fenced tables, no shared liquidity and a longer transition for operators that can prove compliance.
The province’s new online gambling market opens on 13 July, but regulated poker is set to start with Alberta-only player pools.
The company says the province’s market may not be viable unless players can be pooled across provincial borders.