The European Securities and Markets Authority (ESMA) said on September 11 that prediction platforms including Polymarket and Kalshi lack required authorization to offer event contracts to users in the European Union. The bloc's top markets regulator questioned whether partial geo-blocking is sufficient for compliance and noted that event contracts can qualify as financial instruments under MiFID II, triggering stricter oversight requirements.

ESMA's warning changes the calculation for Polymarket and Kalshi as they weigh international expansion against mounting U.S. legal costs. Neither platform holds a MiFID II license, so European access faces a hard stop unless they register or rebuild products to fit exemptions. That licensing process spans months and demands capital reserves no U.S. venue currently maintains. The timing stings: Kalshi and Polymarket built European brand awareness through unlicensed reach, and any formal EU entry now starts with regulatory debt. Institutional partners who already hesitate over U.S. state fights will add Brussels uncertainty to their risk models. For traders, an EU that mirrors U.S. fragmentation means another jurisdiction where contract legality shifts by geography. A MiFID II filing by either platform would signal seriousness, but neither has filed yet.