A judge in New York ordered daily fantasy sports websites FanDuel and DraftKings to stop operating in the state.
The sites had spent more than $100 million on TV advertising, mostly during NFL football games this year and the ruling is likely to close off that spigot.
New York’s attorney general Eric Schneiderman charges that daily fantasy sports amounts to illegal gambling. The judge granted an injunction that prevents the sites from operating until that issue is decided.
Other states have looked at fantasy sports differently. Nevada for one has banned the activity.
The sites have been backed by some of the leagues, team owners and major media companies.
"We are disappointed with the Court's decision, and will immediately file an emergency notice of appeal in order to preserve the status quo," said DraftKings attorney David Boies following the ruling. "Daily Fantasy Sports contests have been played legally by New Yorkers for the past seven years and we believe this status quo should be maintained while the litigation plays out."