South Korean Police Identify Polymarket Users via Blockchain

South Korean authorities have used open‑source analysis of public blockchain data to pinpoint users of the prediction‑market platform Polymarket and charge them with illegal gambling. The investigation began in March, led to 26 bookings by mid‑September, and prompted a nationwide block of the service.

Investigation timeline and outcomes

The Gangwon Provincial Police Agency’s cyber investigation unit opened a preliminary inquiry in March 2026 and started booking suspects in May. By September 15, 26 individuals had been booked, and 18 were referred to prosecutors. The combined value of the stakes involved was approximately $12.7 million (KRW 17.6 billion), with the largest single trader staking about $4.1 million (KRW 5.7 billion).

How suspects were identified

Polymarket operates as a non‑custodial, peer‑to‑peer market that does not maintain a real‑name user list. Police therefore relied on the transparency of blockchain transaction records, applying open‑source intelligence techniques to link wallet addresses to individual traders.

Legal basis for the charges

Authorities charged the users under Article 246 of Korea’s Criminal Act, which criminalizes illegal gambling. Korean Supreme Court precedent allows a gambling conviction when chance plays any role, even if skill influences the outcome. Police argued that the prediction contracts resemble gambling rather than regulated derivatives, citing the lack of specific regulatory guidance.

Regulatory response and broader impact

On August 18, Korea’s broadcasting and communications standards body ordered a complete block of Polymarket, citing a winner‑take‑all payoff structure that users cannot control. Polymarket’s defenses – no Korean language, no won payments, and non‑custodial operation – were rejected. The Korean approach of targeting participants is relatively novel, though similar actions have occurred in Japan against crypto‑based online casinos.

International context

Polymarket has faced regulatory scrutiny elsewhere, including ISP shutdowns in Czechia, a ban in Romania, and a €487,000 penalty from Dutch regulators. The Korean case adds to the growing global debate over whether prediction markets constitute gambling or crypto‑based derivatives.