A federal judge in Arizona has granted an injunction blocking Attorney General Kris Mayes from pursuing a criminal case against prediction market platform Kalshi, a ruling that highlights the complex legal issue that could end up before the nation’s top court.

U.S. District Court Judge Michael Liburdi issued the order May 5 preventing Mayes’ case or any enforcement action from the Arizona Department of Gaming. Mayes filed the nation’s first criminal charges against Kalshi in March, escalating the legal battle over whether the prediction market platform offers gambling or federally regulated trades.

In granting the injunction, Liburdi found the federal government was likely to succeed in its argument that wagers made on Kalshi are not gambling but swaps that are exclusively regulated by the Commodity Futures Trading Commission. The commission filed the case against Arizona, which Liburdi merged with a similar case previously filed by Kalshi.