TLDR
- Detroit plans to file an amicus brief in the Coinbase vs. Michigan prediction markets case, becoming the first U.S. city to enter such litigation
- The city is home to three commercial casinos that generated over $100 million in monthly revenue in early 2026
- Coinbase filed suit after partnering with Kalshi, arguing Michigan gambling laws shouldn’t apply to federally regulated event contracts
- Michigan’s attorney general has also taken enforcement action against Kalshi, Polymarket, and Robinhood
- Baltimore recently sued six sweepstakes casino operators, showing a broader trend of cities getting involved in gaming enforcement
Detroit is set to become the first U.S. city to step into the legal fight over prediction markets. The city plans to file an amicus curiae brief in the case between Coinbase and Michigan state officials.
According to a March 26 filing, Detroit has asked for permission to submit its brief by April 3. The move signals that the city believes it has a direct stake in how prediction markets are regulated under state law.
Detroit is one of Michigan’s biggest gaming hubs. The city is home to three commercial casinos that are regulated by the state.
Those casinos brought in more than $100 million in monthly revenue in both January and February of this year. The state collected over $24 million in taxes from those operations during that period.
The city may view unregulated prediction market platforms as a threat to its established casino industry. As these platforms begin to look more like traditional betting products, local governments with ties to gaming revenue are paying closer attention.
Coinbase and Kalshi at the Center of the Michigan Case
Coinbase is at the heart of this legal dispute. The company filed a lawsuit seeking to stop Michigan officials from applying state gambling laws to federally regulated event contracts.
The suit came just one day after Coinbase announced it was entering the prediction market space through a partnership with Kalshi. Coinbase has argued that Michigan’s enforcement stance could expose the company to civil and criminal liability.
Michigan officials have pushed back. They say that contracts tied to sports fall under the state’s existing gambling laws.
Tribal gaming groups in the state have also weighed in on Michigan’s side. They argue that Coinbase’s position could disrupt the state-tribal agreements that govern regulated sports betting.
Coinbase is not the only company challenging Michigan. Earlier in March, Attorney General Dana Nessel filed a civil enforcement action against Kalshi.
One day later, Polymarket filed its own lawsuit against Nessel and the state. Robinhood followed with a federal lawsuit on the same day, seeking declaratory and injunctive relief.
A federal judge denied Polymarket’s request for a temporary restraining order on March 10. That ruling allowed the state to continue its enforcement efforts. There have been no major updates in the other cases since then.
Cities Push Into Gaming Enforcement Nationwide
Detroit is not the only city taking action on gaming-related issues. Baltimore recently filed a lawsuit against six sweepstakes casino operators.
The Baltimore suit alleges those platforms are running illegal online gambling under Maryland law. The city claims the operators violated its Consumer Protection Ordinance by offering casino-style games in a state where online casino gambling is not legal.
The sweepstakes industry’s “dual-currency” model is at the center of Baltimore’s case. That model has come under growing scrutiny from lawmakers across the country.
Multiple states have moved forward with legislation aimed at banning sweepstakes casinos. While Baltimore’s case does not involve prediction markets directly, the trend shows cities are becoming more active in gaming enforcement.
Detroit’s planned filing in the Coinbase case is expected by April 3, according to the court documents submitted on March 26.
