Wisconsin Sues Coinbase and Polymarket, Alleging Illegal Gambling by Prediction Markets

Decentralized prediction market Polymarket has been hailed as a truth machine. But a recent dispute over a contract asking whether MicroStrategy had sold Bitcoin exposed how such platforms’ determinations of fact can be highly vulnerable to after-the-fact rule interpretations, biased oracle voting and manipulation by large traders. It has also revived a regulatory debate over whether prediction markets should be treated as online gambling or financial derivatives venues.

The dispute began in May 2026, when MicroStrategy sold 32 Bitcoin before the May 31 deadline but did not report the transaction until June 1. Polymarket subsequently changed the rules and resolved the market as “No,” prompting fierce investor backlash. In July 2026, several traders who had backed “Yes” filed a class-action lawsuit against the platform in New York, alleging breach of contract and fraud and accusing it of depriving investors of legitimate gains through a biased decision.

Kalshi and Polymarket allow users to trade contracts tied to game outcomes, point spreads and player statistics. The dispute centers on whether these products are derivatives subject exclusively to oversight by the U.S. Commodity Futures Trading Commission, or must also comply with state gambling laws. Kentucky separately enacted legislation in April 2026 imposing a 14.25% tax on platform trading fees, above the 9.75% rate on racetrack wagers.

On June 17, 2026, Kentucky Attorney General Russell Coleman sued Kalshi, Polymarket and their partners Coinbase, Robinhood and Webull in Franklin Circuit Court, alleging that they offered sports betting without licenses and failed to provide support for problem gambling. The state described the two platforms as multibillion-dollar businesses. The case puts the Trump administration, which supports exclusive federal oversight, in direct conflict with a Republican-led state government.

Prediction markets allow users to trade contracts tied to the outcomes of elections, economic developments, sporting events and other occurrences. Kalshi, Polymarket and Crypto.com are all major platforms. Kentucky is the first state to impose a dedicated tax on such trades, a move that could affect platforms’ operating costs and shape whether other states can follow suit, as well as the boundaries of federal regulatory authority.

As of July 20, 2026, the three companies had formed a coalition and filed suit in a Kentucky court to challenge the state’s first-of-its-kind 14.25% tax on prediction-market trades. The companies argue that the tax subjects prediction markets to disparate treatment, making it discriminatory and unconstitutional. Available information has not disclosed the exact filing date, the damages sought or the date of the first hearing.

Prediction markets allow users to trade event contracts tied to outcomes such as elections and sporting events. The central dispute is whether these products are derivatives governed by the Commodity Exchange Act or wagers that states may regulate under gambling laws. The U.S. Commodity Futures Trading Commission argues that event contracts traded on designated contract markets fall under its exclusive federal jurisdiction. The ruling will affect whether platforms can operate across states under a single set of rules.

The Wisconsin Department of Justice sued five companies—Kalshi, Polymarket, Crypto.com, Robinhood and Coinbase—on April 23, 2026, accusing them of illegally offering sports betting. On April 28, the CFTC, together with the U.S. Department of Justice, filed suit in federal court in Wisconsin's Eastern District. It was the agency's fifth similar lawsuit against a state government. The complaint seeks a declaration that state gambling laws do not apply and a permanent injunction barring state enforcement, but requests no damages.

Prediction markets allow users to trade contracts based on event outcomes. Operators argue that they should be regulated by the U.S. Commodity Futures Trading Commission under federal derivatives law, while New York considers contracts tied to sports, entertainment and elections to be gambling. Gemini launched its service nationwide in December 2025, followed by Coinbase in January 2026. Their failure to obtain licenses from the New York State Gaming Commission has put them at the center of a state-federal jurisdictional dispute.

On April 21, 2026, New York Attorney General Letitia James sued Coinbase Financial Markets and Gemini Titan in state court, alleging that the platforms allowed users as young as 18, below the state's minimum age of 21 for mobile sports betting. The state is seeking to halt their operations, recover profits, obtain $100,000 for each violation and impose penalties equal to three times their unlawful gains. Coinbase moved the case to federal court on April 22.

Prediction markets allow users to trade contracts tied to the outcomes of political, economic and other events, and are legally classified as derivatives in the United States. After Coinbase launched its service in partnership with CFTC-regulated Kalshi, state governments continued to argue that the contracts constituted gambling. The dispute centers on whether federal commodities law preempts state regulation.

Coinbase Head of Litigation Ryan VanGrack accused multiple states of misleading the public and called claims that the CFTC was incapable of regulating the markets “gaslighting.” Coinbase has sued governments including Illinois and Connecticut, seeking court rulings affirming the CFTC's preemptive jurisdiction. Detroit is also preparing to join Michigan's legal battle.

Prediction markets allow users to trade contracts on election, economic or sports outcomes. Operators including Kalshi and Polymarket argue that their products are derivatives regulated by the CFTC, while states view proposition wagers as gambling, creating a jurisdictional clash between federal commodities law and state gaming laws.

The Utah Legislature passed HB243 in 2026, classifying proposition wagers on event outcomes as illegal gambling and barring operators from offering sports-betting-like prediction services in the state. Governor Spencer Cox has said he will sign the bill, exposing Kalshi and Polymarket to the risk of being blocked and facing enforcement action.