The NFL is asking the Supreme Court to allow states to regulate prediction markets as a form of gambling, filing an amicus brief Thursday in support of New Jersey regulators as the state looks to take the fight between states and Kalshi to the nation’s highest court.

“At present, prediction markets continue to lack the regulatory requirements necessary to protect the integrity of the game and consumers,” said a league source within the NFL, who spoke on condition of anonymity because they were not authorized to speak publicly on the matter.

Last Sunday, trading on the NFL made up 65.8 percent of Kalshi’s sports volume, according to Ticker Tracker, a website that tracks prediction market trading.

Currently, prediction markets are regulated by the Commodity Futures Trading Commission (CFTC) at the federal level, similarly to the stock market, which means companies such as Kalshi and Polymarket are not subject to state-specific gambling regulations as sportsbooks are. But 20 states have argued in the courts that prediction markets should be subject to state rules. For example, the legal age for sportsbooks in most states is 21, but 18 across the country for prediction markets.

A spokesperson for Kalshi said that it “consistently tried to engage proactively and constructively with the NFL to collaborate on market integrity with no response.”

Brooke Nethercott, public affairs director at the CFTC, said the Commission has engaged with the NFL “since day one.”