The law in question, Senate Bill 3019, was signed by Pritzker on June 16 as part of Illinois's approximately $55.9 billion fiscal year 2027 budget package. It classifies sports-event contracts on prediction market platforms as sports wagering and places oversight authority with the Illinois Gaming Board. Operators seeking to serve Illinois residents would need a "master prediction market license" costing $1 million to obtain and another $1 million annually to renew. On top of that, the law imposes a 50% tax on adjusted gross receipts plus a per-transaction tax: 1.75% on the first five million wagers per year and 3.5% on any volume beyond that threshold. Illinois is only the second U.S. state to enact explicit prediction markets legislation, after Minnesota, making the lawsuit a nationally significant test of whether states can regulate federally licensed prediction market operators.

Kalshi's core legal argument rests on the Commodity Exchange Act (CEA), the federal statute that grants the Commodity Futures Trading Commission (CFTC) exclusive jurisdiction over derivatives traded on designated contract markets. The company advances three distinct preemption theories. First, under express preemption, Kalshi argues that Illinois is attempting to regulate instruments that Congress has explicitly placed under federal authority. Second, under field preemption, federal courts have warned against allowing states to recreate the regulatory "patchwork that Congress replaced wholecloth" when it established the CFTC's exclusive framework. Third, under conflict preemption, Kalshi argues that because the CFTC requires designated contract markets to provide impartial, nationwide access to traders, it cannot selectively block Illinois users without violating its federal obligations. Complying with Illinois, the company says, would require it to violate federal law. Refusing to comply would expose it to state enforcement.

Kalshi is not alone in this fight. In April 2026, the CFTC and the Department of Justice filed simultaneous separate lawsuits against Illinois. It was the first time the federal government, through the DOJ, had sued states over prediction markets. The CFTC later amended its complaint in June to specifically challenge the new transaction tax provisions in SB 3019. Federal regulators have argued the 3.5% per-transaction rate would likely meet or exceed the fees exchanges themselves charge, effectively functioning as a ban rather than a tax.

The broader landscape of state hostility toward prediction markets extends well beyond Illinois. In March 2026, Arizona filed 20 criminal misdemeanor charges against KalshiEX LLC, described by legal observers as the most extreme state action against a prediction market operator to date. Thirty-four states have filed amicus briefs supporting state authority over prediction markets, signaling that this is not an isolated dispute but a coordinated effort by state governments to assert regulatory control over a fast-growing sector.

The Third Circuit Court of Appeals handed Kalshi a significant legal win in April 2026, ruling two to one in KalshiEX LLC v. Flaherty that the CEA gives the CFTC exclusive jurisdiction over Kalshi's sports-event contracts. That ruling creates favorable precedent, but it is not binding outside the Third Circuit. Courts in other jurisdictions have reached opposite conclusions, including the Suffolk County Superior Court in Massachusetts in January 2026 and a U.S. District Court in August 2025. Legal analysts at Epstein Becker Green and Holland and Knight consider a U.S. Supreme Court petition virtually inevitable given the widening split between courts.

Illinois officials have not backed down. Pritzker's office has previously accused prediction market platforms of facilitating insider trading schemes, describing the companies as "carrying water for companies driving well-documented and lucrative insider trading schemes." Connecticut Attorney General William Tong, whose state faces a parallel federal lawsuit, dismissed the federal and Kalshi lawsuits as "recycled industry arguments."

The federal government's aggressive posture toward prediction market opponents also carries a notable political dimension. Donald Trump Jr. serves as a strategic advisor to both Kalshi and Polymarket, and the Trump administration dropped its original Kalshi appeal in May 2025, signaling federal alignment with Kalshi's position before the DOJ later joined the lawsuits directly. That background helps explain the intensity with which federal authorities have intervened on behalf of a private exchange.

The scale of what is being contested is substantial. Kalshi recorded roughly $17.9 billion in trading volume in May 2026, representing approximately 57% of the prediction market sector by volume. Polymarket, its largest competitor, logged about $7.1 billion in the same period. Analysts have projected total prediction market volume could reach $240 billion for full-year 2026, roughly 3.7 times the 2025 figure. Polymarket operates on Polygon, an Ethereum Layer-2 blockchain, and settles trades in USDC, a dollar-pegged stablecoin. Because its core contracts run on public blockchain infrastructure, it is partially insulated from the kind of state-level enforcement that targets centralized platforms. Kalshi, by contrast, is a fully centralized, CFTC-licensed exchange with no blockchain component, which makes it more directly exposed to state regulatory actions.

For users and developers outside the United States, the stakes in this dispute extend well beyond Illinois. In Nigeria, where Polymarket is accessible and where crypto adoption ranks among the highest in the world by peer-to-peer volume according to Chainalysis, the question of whether prediction market contracts are derivatives or gambling has direct regulatory parallels. Nigeria's Securities and Exchange Commission has yet to issue clear guidance on crypto derivatives. In India, similar tensions between central and state authority over financial contracts have surfaced in debates over exchange-traded derivatives and crypto regulation. India's Securities and Exchange Board (SEBI) and the Reserve Bank of India (RBI) are both navigating questions about whether event contracts fall under the Securities and Contracts Regulation Act (SCRA) or constitute a form of gambling, and Indian fintech operators such as Probo are already watching the outcome of Kalshi's election contract approvals closely. In Kenya, Polymarket is blocked entirely, a notable contrast with Nigeria given Kenya's large mobile money and crypto-literate population. South Africa's Financial Sector Conduct Authority has issued crypto licensing frameworks but has not addressed event contracts. A U.S. Supreme Court ruling that sides with states would fragment the American market and signal to regulators globally that sub-national authorities can override federally licensed exchanges, a precedent with far-reaching consequences for any market where the regulatory classification of event contracts remains unsettled.

Legal analysts expect Kalshi to seek a preliminary injunction before the July 1 compliance deadline. A U.S. District Court in Tennessee already granted Kalshi a preliminary injunction in February 2026, and analysts at Epstein Becker Green and Holland and Knight say the company has credible grounds to pursue similar relief against the Illinois law. Whether any such relief survives appellate or Supreme Court review is an open question, and one that prediction market operators and their users worldwide will be watching closely.