Detroit Lawyers File Amicus Brief Supporting Michigan’s Motion to Ban Coinbase

Detroit attorneys have received court approval to file an amicus curiae brief supporting Michigan’s effort to block Coinbase from operating its prediction markets service in the state, marking the first time a U.S. city has formally intervened in the escalating legal battle over whether prediction markets are gambling or federally regulated financial products.

U.S. District Court Judge Shalina Kumar of the Eastern District of Michigan granted the request, giving Detroit’s legal team until April 3 to submit the brief. The filing will support Michigan state authorities in their opposition to Coinbase’s motion for a preliminary injunction against state enforcement of gambling regulations on prediction markets.

It is worth clarifying that Michigan’s legal action targets Coinbase’s prediction markets feature specifically, not the exchange as a whole. The state is seeking a preliminary injunction to block the prediction markets service, not a blanket ban on Coinbase operations in Michigan.

Detroit Lawyers Join Michigan’s Legal Push Against Coinbase

Detroit’s decision to file an amicus brief, a “friend of the court” filing from a party not directly involved in the case, carries unusual weight. The city is home to all three of Michigan’s commercial casinos, giving it a direct financial interest in how the state regulates gambling-adjacent products.

Those three casinos generated over $200 million in revenue during January and February 2026 alone, contributing more than $24 million in state taxes over the same period. If prediction markets expand without state oversight, Detroit stands to lose a share of that revenue to unregulated competitors.

Detroit Casino Revenue (Jan–Feb 2026)

$200M+

Revenue generated by Detroit’s 3 commercial casinos, yielding $24M+ in state taxes — the financial stake behind Detroit’s amicus brief supporting Michigan’s bid to block Coinbase prediction markets.

Detroit is the first U.S. city to formally enter the growing legal dispute over prediction markets by filing an amicus brief. The move could set a precedent, potentially encouraging other gambling-dependent cities like Las Vegas or Atlantic City to file similar briefs in their respective states.

The Legal Theory: CFTC Jurisdiction vs. State Gambling Law

At the core of this case is a jurisdictional question. Coinbase argues that prediction markets are event contracts regulated by the U.S. Commodity Futures Trading Commission (CFTC), which would preempt state gambling laws. If the court agrees, states would lose their ability to regulate or restrict prediction markets platforms.

Michigan’s gambling regulators take the opposite view, contending that prediction markets function as gambling products and fall squarely under state oversight. The state’s motion for a preliminary injunction seeks to block Coinbase from offering its prediction markets service to Michigan residents while the case proceeds.

Coinbase filed pre-emptive lawsuits in December 2024 against gaming authorities in three states: Michigan, Connecticut, and Illinois. The exchange took that step more than a month before launching its prediction markets product, a move designed to establish legal precedent before regulators could act. Michigan’s counter-motion, now supported by Detroit’s amicus brief, is the most aggressive state-level response to date.

If the court grants Michigan’s preliminary injunction, Coinbase would be barred from offering prediction markets to Michigan users while the underlying case is litigated. For users already on the platform, this could mean forced position closures or geographic restrictions similar to those exchanges have implemented in response to other regulatory actions targeting Coinbase.

Why an Amicus Brief Matters More Than It Sounds

An amicus curiae brief is not a party filing in a lawsuit. It is a submission from an outside entity that the court is not required to consider, but often does when the filer brings relevant expertise or a unique perspective.

Detroit’s filing carries particular significance because it demonstrates that the consequences of this case extend beyond abstract regulatory turf wars. A city government with hundreds of millions in casino-related revenue at stake provides the court with a concrete, financially quantifiable argument for why state oversight matters.

Courts have historically given weight to amicus briefs when they introduce evidence or perspectives that the primary parties have not raised. In high-profile regulatory cases, coalition amicus filings, where multiple parties submit briefs on the same side, can signal to judges that a ruling will have broad real-world consequences beyond the two litigants.

Stephen Piepgrass, an attorney at Troutman Pepper Locke, noted the broader jurisdictional implications of how the CFTC positions itself in these disputes.

That observation highlights the strategic calculus for both sides. The more active the CFTC is in regulating prediction markets, the stronger Coinbase’s federal preemption argument becomes. Conversely, if the CFTC remains passive, states like Michigan have a stronger claim that their gambling laws fill the regulatory vacuum.

A National Pattern: Prediction Markets Under Fire Across Multiple States

Michigan is not acting in isolation. Prediction markets face a patchwork of legal challenges across the United States, and the pace of litigation has accelerated significantly in early 2026.

In February, a Tennessee judge blocked state enforcement against a prediction markets platform, ruling in favor of federal preemption. In March, a Nevada judge took the opposite approach, ordering a temporary halt to a platform’s operations. Also in March, Arizona filed criminal charges against a prediction markets operator, the most aggressive enforcement action to date.

These conflicting rulings across different states create what legal analysts call a “circuit split” scenario. When federal courts in different jurisdictions reach opposing conclusions on the same legal question, the U.S. Supreme Court often steps in to resolve the conflict.

Legal experts have noted that this cluster of prediction markets cases may ultimately reach the Supreme Court, particularly given its 2018 decision in Murphy v. NCAA. That ruling granted states the authority to regulate sports gambling, a precedent that Michigan and other states are now invoking to argue they can also regulate prediction markets. The broader regulatory environment for crypto continues to evolve as these cases work through the courts.

Coinbase’s position is that prediction markets are fundamentally different from sports gambling. The exchange contends that event contracts, which allow users to bet on the outcome of real-world events, are financial derivatives regulated by the CFTC under the Commodity Exchange Act. State gambling commissions, in this view, have no more authority over prediction markets than they do over futures contracts on corn or oil.

What Happens Next: Key Dates and Possible Outcomes

The immediate next step is the April 3 deadline for Detroit’s lawyers to submit their amicus brief. Once filed, Coinbase will have an opportunity to respond to both the brief and Michigan’s underlying motion for a preliminary injunction.

Judge Kumar will then decide whether to grant the preliminary injunction. If granted, Coinbase would be temporarily barred from offering prediction markets in Michigan while the full case proceeds, a process that could take months or years. If denied, Coinbase’s prediction markets would continue operating in the state during litigation.

Coinbase has not publicly detailed its defense strategy for the Michigan case specifically, but the exchange’s broader legal approach has been to pursue federal preemption arguments across all three states where it filed suits. The December 2024 lawsuits in Michigan, Connecticut, and Illinois were designed to establish favorable precedent before state regulators could act.

The outcome in Michigan could influence how other states approach prediction markets regulation. A ruling that state gambling laws apply to prediction markets would embolden regulators in states that have been watching from the sidelines. A ruling favoring federal preemption would weaken state-level enforcement efforts nationwide. Recent developments across the crypto industry suggest that regulatory clarity, wherever it comes from, will shape the competitive landscape for exchanges.

No U.S. state has successfully imposed a permanent ban on a major crypto exchange to date, though several have imposed operating restrictions. The Michigan case, amplified by Detroit’s amicus brief, represents one of the most substantive state-level challenges to a specific exchange product in recent history.

FAQ: Michigan’s Motion Against Coinbase Prediction Markets

What is an amicus brief and why does it matter here?

An amicus curiae (“friend of the court”) brief is a legal filing from an entity that is not a party to the lawsuit but has relevant expertise or interest in the outcome. Detroit’s brief matters because it introduces the city’s direct financial stake, over $200 million in casino revenue, as evidence that prediction markets regulation has real economic consequences for local governments.

Can Michigan legally ban Coinbase from operating in the state?

Michigan is not seeking to ban Coinbase entirely. The state’s motion targets Coinbase’s prediction markets feature specifically, arguing it constitutes unregulated gambling under state law. If the court grants the preliminary injunction, Coinbase would be blocked from offering prediction markets to Michigan residents, but other exchange services could continue.

What happens to Coinbase users in Michigan if the motion succeeds?

If the preliminary injunction is granted, Michigan-based users would likely lose access to Coinbase’s prediction markets product. Existing positions could be subject to forced closure or withdrawal. Other Coinbase services, such as spot trading and custody, would not be directly affected by this specific motion.

Has any U.S. state successfully banned a major crypto exchange before?

No state has imposed a permanent, full-service ban on a major crypto exchange. However, several states have restricted specific products or required exchanges to obtain state-level licenses. The Michigan case is notable for targeting a specific product category, prediction markets, rather than exchange operations broadly.

Disclaimer: This article is for informational purposes only and does not constitute financial or investment advice. Cryptocurrency and digital asset markets carry significant risk. Always do your own research before making decisions.