South Korean police referred 18 Polymarket users to prosecutors without detention after investigating 26 people over suspected illegal gambling linked to combined wagers of 17.6 billion won ($12.7 million). The largest amount attributed to one user was 5.7 billion won ($4.1 million). Authorities blocked domestic access to Polymarket on Aug. 18, treating its event contracts as illegal gambling under South Korean law despite users' argument that the tradable contracts resemble crypto-based derivatives. The case highlights a wider regulatory divide: South Korea is pursuing participants under gambling rules, while the U.S. has a federal derivatives-market framework for designated contract markets including Kalshi. South Korea's status as a major retail crypto market, combined with Polymarket's omission from its published blocked-country and close-only lists, underscores compliance risks for platforms operating across jurisdictions.