A new federal tax rule is already shrinking poker schedules.

Poker Hall of Famer Erik Seidel told CNBC recently that he is skipping bigger buy-in tournaments because the incoming rule will make high-volume poker harder to justify.

"This just creates a situation where it's really untenable," Seidel said.

Under the new rule, gamblers will be able to deduct only 90% of losses against winnings, down from 100%, meaning players could owe taxes on money they never actually kept.

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