The NFL has taken a side in the growing legal fight over prediction markets, coming out in support of New Jersey against Kalshi and filing an amicus brief Thursday asking the Supreme Court to review the case.

The league argues that sports contracts constitute gambling, and that letting prediction markets offer them outside state gambling laws threatens game integrity and consumer protections.

It’s a steep escalation from the NFL, which has spent months raising concerns with prediction markets directly while also exploring partnerships with them.

And with the NBA also weighing its own prediction market deals ahead of its October 20th season opener, its decision could add further pressure on the Supreme Court to take up the case.

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Months of Friction

The filing follows back-and-forth between the NFL and both Kalshi and Polymarket over which contracts should be allowed on their platforms.

In March, the league sent letters to prediction market operators asking them to prohibit bet types it considered particularly vulnerable to manipulation: contracts such as those tied to player injuries, officiating decisions, or individual plays a single person could influence.

The league also pressed the CFTC to introduce stronger safeguards in May and argued in July that the agency’s proposed rules fell short of protections already required of traditional sportsbooks.

By September, the NFL was reiterating its complaints, saying contracts it had flagged months earlier were still being offered, while also keeping the door open to commercial partnerships. According to Front Office Sports, the league had been holding discussions with Kalshi, Polymarket, and the CFTC for months, though no partnership materialized before the season began.

In a CNBC interview published September 11, Commissioner Roger Goodell confirmed the league was still speaking with operators about changes that could make them potential partners.

The NFL had cited inadequate regulation and legal uncertainty as reasons it wasn’t ready to sign a deal, though the details of its private discussions remain unclear. Such a partnership could still give the NFL more direct involvement in monitoring market integrity, along with licensing, data, and marketing arrangements.

Even so, the league has now backed New Jersey’s argument that federal commodities law does not stop states from regulating sports-event contracts as gambling.

As we covered previously, federal appeals courts are already split on that question, with the Third Circuit backing Kalshi and the Sixth and Ninth Circuits siding against it.

The Supreme Court has not yet agreed to hear the case.

A Split Among Leagues

The NFL’s position contrasts with several other major sports organizations that have embraced prediction markets.

The NHL partnered with both Kalshi and Polymarket last October, while UFC and MLS subsequently signed agreements with Polymarket. In March, MLB followed, partnering with Polymarket and signing a separate agreement with the CFTC to strengthen market integrity.

Meanwhile, the NFL has stuck with traditional sportsbook partnerships, renewing deals with DraftKings and FanDuel while adding Fanatics in August.

Funnily enough, DraftKings, FanDuel, and Fanatics also operate prediction market products, meaning the NFL’s partners are building businesses in the market whose regulation the league is challenging.

That market is also sizable. In Thursday’s brief, the NFL said that $1.8 billion of the $3.3 billion traded on prediction markets during the season’s opening Sunday involved NFL games, more than half of that day’s trading.

And while the NFL has taken its position to the Supreme Court, the NBA remains undecided.

In September, Front Office Sports reported that the league had circulated partnership proposals to several operators, including Kalshi, Polymarket, and Fanatics, with deal terms reportedly on the table.

But the NBA has also spent more than a year raising similar regulatory concerns. In May 2025, it called for stronger oversight of prediction markets, and as recently as July, argued that proposed CFTC rules fell short of basic protections against insider trading and market manipulation.

Yet like the NFL before Thursday, the NBA has stopped short of siding with states on the legal question. In April, it explicitly declined to take a position on whether sports prediction markets legally constitute gambling.

The NFL followed a similar path, pushing for stronger regulation while exploring partnerships. With no deal reached before kickoff, the league has now taken that next step.

With NBA opening night approaching, the question is whether the league follows suit.

If a partnership comes together, the NFL would remain a notable holdout among these major leagues, though an NBA deal wouldn’t necessarily mean abandoning its regulatory concerns.

But if talks stall, the NBA could follow the NFL in backing the states, given its own longstanding concerns about market integrity. That would put both leagues on the same side against Kalshi’s claim that federal law overrides state gambling rules, adding weight to the push for Supreme Court review.

The NBA could also continue pressing for stronger rules without taking a legal position. But after watching the NFL move from regulatory complaints to a Supreme Court filing, another major league following its lead is becoming harder to ignore.