Bitbank Warns Japanese Users: Polymarket Access Could Lead to Account Suspension Under Gambling Laws

Bitbank, one of Japan’s licensed cryptocurrency exchanges, has drawn an unusually sharp line against offshore prediction market platforms. In a recent caution, the exchange warned that Japanese residents who use services such as Polymarket for monetary gain may be considered to be engaging in gambling. The consequences are not abstract: accounts suspected of interacting with these markets face outright suspension, cutting off crypto deposits, withdrawals, yen withdrawals, and trading entirely.

The notice, published by the exchange and covered in the original report, signals a compliance posture that could ripple through Japan’s tightly regulated crypto sector. By linking prediction market activity to Japan’s penal code gambling provisions, Bitbank is essentially treating a new wave of DeFi-adjacent platforms as a direct legal risk for its users and itself.

Japan’s Gambling Laws Meet Offshore Prediction Markets

Polymarket operates on the Polygon network and does not directly serve Japanese customers in a licensed capacity. But any user with a crypto wallet can interact with its smart contracts, and the platform’s global reach has long put it in a legal gray zone for jurisdictions with strict gambling laws. Japan’s Criminal Code prohibits most forms of gambling, with limited exceptions for publicly operated betting on horse racing, bicycle racing, motorboat racing, and a few other activities. Peer-to-peer prediction markets like Polymarket do not fit into those exceptions.

Bitbank’s warning makes clear that the exchange will monitor deposits and withdrawals for links to prediction markets or services it suspects are connected to them. It is a notable escalation, because until now the enforcement focus in Japan has been on unregistered crypto exchanges, not on end-user behavior involving DeFi protocols. The statement suggests regulators may be pressuring licensed platforms to act as gatekeepers.

Account Suspension and Service Restrictions

The operational impact for affected users is severe. Once an account is flagged and suspended, the holder loses the ability to log in, move crypto assets, withdraw Japanese yen, or execute any crypto trades. Bitbank framed the measure as necessary to prevent illegal activity, but for a trader who moves funds between a Polymarket wallet address and their exchange account, the policy turns a transaction into a potential account death sentence.

This is not a block on a specific cryptocurrency. The exchange did not announce any asset delistings or restrictions on the MATIC token, which is used for Polymarket fees. Instead, the policy targets behavioral patterns, on-chain forensics, and possibly customer disclosures. Other Japanese exchanges have not yet made similar public statements, though industry insiders are watching whether the Financial Services Agency (FSA) will issue broader guidance.

A Wider Regulatory Squeeze

The Bitbank move arrives against a global backdrop where regulators are increasingly scrutinizing crypto platforms that blend trading with gambling-like features. In the United States, the debate is different but related—lawmakers have clashed over what qualifies as a securities contract, and banking interests are actively trying to shape the legislative outcome. A landmark crypto bill facing fierce banking opposition in the US shows how traditional finance is fighting to control the classification perimeter. In Japan, the fight is about something simpler: whether interacting with a smart contract for a wager amounts to criminal conduct.

Prediction markets have seen explosive global volume, with Polymarket handling billions in notional value across elections, geopolitics, and pop culture. For an exchange like Bitbank, the volume itself is not the problem—it’s the legal exposure. If the FSA eventually rules that deposits originating from prediction market wins are proceeds of illegal gambling, exchanges could be accused of handling tainted funds. The reputational risk alone is enough to trigger preemptive action.

What Remains Unclear

Bitbank did not publish a definitive list of flagged services beyond referencing “prediction market services, including Polymarket.” That leaves room for confusion around other platforms like Augur, SX Bet, or newer entrants. Traders who move funds through non-custodial wallets before touching a Japanese exchange might also wonder how deep the tracing goes, and whether the exchange’s compliance screening will catch peer-to-peer transactions that are not obvious on-chain.

The bigger uncertainty is whether other licensed exchanges will follow with identical policies. Japan’s self-regulatory crypto body, the Japan Virtual and Crypto Assets Exchange Association (JVCEA), often coordinates policy enforcement among members, but no public statement has emerged from the group. Users are essentially left guessing about which behaviors will trigger a freeze at which platform. For a market that prizes permissionless access, the Bitbank notice is a reminder that the path back into fiat is where national law still bites hardest.