The FBI raided Shayne Coplan's New York apartment in November 2024 using a battering ram, searching for evidence of illegal betting on Polymarket. Agents seized devices as part of an investigation into whether the prediction market platform allowed U.S. users despite being barred.

Months earlier, Kalshi lawyers met with federal prosecutors in Manhattan and explained that Polymarket users could still access the platform from the United States. Tarek Mansour, Kalshi's CEO, had become Coplan's fiercest rival in the fast-growing prediction market sector.

Coplan publicly cast the raid as a Biden administration attack but privately suspected Mansour of weaponizing regulators. The feud between the 28-year-old Coplan and 30-year-old Mansour — both newly minted billionaires — has spilled beyond normal startup competition as they fight to dominate the sector.