The state-federal fight over prediction markets escalated on multiple fronts Friday as New York Attorney General Letitia James joined a bipartisan coalition of 37 other attorneys general urging Massachusetts' top court to uphold a preliminary injunction against Kalshi, and the CFTC sued New York later in the day to block state enforcement against CFTC-registered exchanges.

The amicus brief, filed in the Supreme Judicial Court of Massachusetts, asks the court to affirm a January ruling that Kalshi cannot offer sports event contracts to in-state residents without a Massachusetts Gaming Commission license. The signatories span the political spectrum and include attorneys general from 37 states and the District of Columbia.

"Kalshi's event contracts for sports are just illegal gambling by another name, and they should play by the same rules as every other licensed gambling platform," James said in a statement.

According to the brief, Kalshi users wagered more than $1 billion every month on the platform in 2025, with sports betting accounting for roughly 90% of that volume in certain months. The coalition argues Kalshi's contention that its contracts are "swaps" subject to exclusive CFTC oversight under Dodd-Frank misreads the 2010 statute, which the AGs say was crafted to address the financial instruments behind the 2008 crisis, not to legalize sports gambling nationwide at a time when federal law still prohibited states from authorizing it.

CFTC strikes back

Hours later, the CFTC filed its own complaint in the U.S. District Court for the Southern District of New York, naming James, Governor Kathy Hochul, the New York State Gaming Commission, Executive Director Robert Williams, and six commissioners as defendants.

The agency is seeking a declaratory judgment that federal law grants it exclusive authority over event contracts, plus a permanent injunction blocking the state from enforcing what it calls preempted gambling laws against CFTC-registered entities.

"New York is the latest state to ignore federal law and decades of precedent by seeking to enforce state gambling laws against CFTC-registered exchanges," CFTC Chairman Michael Selig said in a statement. The agency cited an October cease-and-desist letter Kalshi received from New York gaming regulators, alongside this week's civil suits against Coinbase and Gemini, as the conduct intruding on federal jurisdiction.

James and Hochul, both Democrats, issued a joint statement Friday evening accusing the Trump administration of "prioritizing big corporations over consumers and New Yorkers' best interests" and pledging to defend the state's gambling laws in court.

The CFTC's New York complaint follows nearly identical suits the agency filed against Arizona, Connecticut, and Illinois on April 2. Selig has steadily expanded the agency's jurisdictional posture since taking over the agency, where he sits as the only current commissioner, withdrawing a Biden-era proposal that would have banned political event contracts and warning state regulators in February that the agency would "no longer sit idly by."

Mixed legal outcomes so far

Arizona, Connecticut, and Illinois, the three states the CFTC is currently suing, all signed onto Friday's brief, as did Tennessee and New Jersey, where federal courts have so far ruled in Kalshi's favor. The breadth of the signatories, drawn from states that have won, lost, or have yet to fight in court, underscores how broadly state attorneys general view the preemption argument as a threat to traditional state authority over gambling.

Court outcomes have been split. The U.S. Court of Appeals for the Third Circuit sided with Kalshi over New Jersey earlier this month in a 2-1 ruling, and a Tennessee federal judge granted the company a preliminary injunction in February. State and federal judges in Nevada, Maryland, Ohio, and Massachusetts, however, have ruled against the platform.

The Friday actions cap a week of cascading enforcement. James sued Coinbase and Gemini on Tuesday, seeking a minimum of $2.2 billion and $1.2 billion, respectively. Wisconsin's attorney general filed civil suits Thursday against Kalshi, Polymarket, Robinhood, Crypto.com, and Coinbase, alleging their sports event contracts violate the state's commercial gambling ban.

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Kalshi was last valued at roughly $22 billion following a $1 billion raise disclosed in March, and recorded over $10 billion in trading volume so far this month, per The Block's data dashboard. TD Cowen analyst Jaret Seiberg has said states still appear to hold the stronger legal position, with the dispute likely heading to the Supreme Court and a resolution potentially not arriving until 2028.