Dutch Regulator Upholds Polymarket Sanction, Rejects the Blockchain Defense

The Dutch gambling regulator has upheld its sanction against Polymarket, ruling that the crypto-based prediction platform offered unlicensed gambling to Dutch players and that its blockchain architecture buys it no exemption from Dutch law. The Kansspelautoriteit (KSA) published the decision on June 23, 2026, rejecting an appeal from Adventure One QSS Inc, the operator behind Polymarket, and leaving intact a penalty order (a last onder dwangsom, or order subject to a periodic penalty) of 420,000 euros per week to a maximum of 840,000 euros (about 483,000 to 966,000 dollars).

The order dates to February 2026, when the KSA told Polymarket to cease serving Dutch customers immediately or start accruing the weekly penalty. The compliance deadline was February 17. Polymarket missed it and only switched on IP-blocking the next day, February 18, the same day the regulator ran a re-inspection and found Dutch users could still reach the markets. That one-day gap was enough to trigger the first tranche: the KSA moved to collect 420,000 euros, which Adventure One declined to pay, prompting a separate enforcement (collection) order before the company lodged its objection in March and asked for its legal costs back. The action is one front in a broader European campaign against prediction markets that has run through 2026.

The chance test beats the code

The appeal turned on a single argument: that Polymarket is not gambling at all, so it needs no Dutch licence. Adventure One said its platform was merely an interface to Polygon, an open-source blockchain protocol, letting users trade peer-to-peer positions from their own crypto wallets, and that in some framings the product is a regulated financial instrument rather than a bet. The KSA rejected the whole chain. It found that the element of chance, sitting beyond the decisive influence of the participant, made the offering a game of chance, and that Polymarket gave Dutch users "an opportunity to compete for prizes or rewards" by wagering on future events, which meets the statutory definition of gambling under Dutch law. Blockchain, crypto wallets and decentralised protocols, it said, do not exempt an operator from that law.

The regulator also used Polymarket's own words against it. Its promotional copy invited users to "stay informed and profit from your knowledge by betting on future events," a line the KSA read as flatly contradicting the claim that no betting was involved. The initial investigation had already established Dutch targeting: registration was open to Dutch IP addresses, customer service ran a Dutch-language AI chat, and users could wager on markets tied to Dutch politics and Dutch sporting figures. Betting on political events is separately prohibited under Dutch gambling legislation. Adventure One's fallback arguments, that the sanction was disproportionate, legally uncertain and inadequately reasoned, were dismissed, as was its complaint that publicly naming the platform was unfair. The KSA cited the Dutch Open Government Act and justified disclosure on consumer protection, transparency and deterrence.

This decision is distinct from the Dutch Supreme Court refund ruling issued weeks earlier, which concerned whether players can claw back losses from pre-2021 unlicensed operators. That case was about historic contracts and civil liability. This one is a forward-looking enforcement action that settles, at the regulator level, whether a prediction market needs a Dutch gambling licence. The KSA's answer is yes.

Europe closes ranks as the money keeps flowing

The ruling lands inside a coordinated European move against the same two US platforms. On June 18, 2026, timed to the opening of the FIFA World Cup, nine regulators from Belgium, France, Germany, Italy, the Netherlands, Poland, Portugal, Spain and Switzerland signed a joint initiative pledging cross-border monitoring, information sharing and enforcement ranging from warnings to site blocking and account freezing. Their stated concerns were round-the-clock access without betting limits or cooling-off periods and weak age and identity checks on unlicensed platforms. The pressure reaches beyond the crypto-native platforms: Germany's GGL has opened an investigation into FIFA partner ADI Predictstreet, which took a gambling licence in Gibraltar earlier this year.

A parallel financial-regulation track is also tightening. The European Securities and Markets Authority has cautioned that prediction products structured as yes-or-no contracts with fixed payouts may qualify as restricted financial instruments and fall under the EU's existing ban on marketing binary options to retail clients, which would box the sector in from a second direction. The pattern of walls going up across Michigan and Europe has been the defining regulatory theme for the sector this year.

The enforcement outcomes elsewhere show what "upheld" tends to mean in practice. The table below tracks the bloc's actions against Kalshi and Polymarket.

The financial framing matters for how seriously operators treat these penalties. A one-week Dutch penalty of 420,000 euros is a rounding error against Polymarket's balance sheet: the company was in talks in April 2026 to raise about 400 million dollars at a 15 billion dollar valuation, up from roughly 9 billion a year earlier, after Intercontinental Exchange (owner of the NYSE) committed 2 billion dollars in total, including a 600 million dollar tranche in March 2026. Rival Kalshi raised 1 billion dollars at a 22 billion dollar valuation and is generating an estimated 1.5 billion dollars in annual revenue. Sector trading volume tripled to 51 billion dollars in 2025, and Bernstein analysts have projected roughly 240 billion dollars in 2026, a forecast that attributes the growth to institutional and retail adoption rather than any single event. Against those numbers, European fines are not a deterrent by size. They are a deterrent by access: a blocked market is a market you cannot monetise, and the KSA decision hardens the legal basis for blocking.

For affiliates and licensed operators, the practical read is jurisdictional. In the Netherlands, where the KOA regime opened in October 2021 and channelisation has slipped to about 49 percent of GGR, the KSA has now made clear it will treat prediction markets as it treats any other unlicensed operator. Sending Dutch traffic to Polymarket or Kalshi is sending traffic to a named, sanctioned, blockable target, and the regulator has signalled it will publish the enforcement. That closes off a would-be prediction-markets affiliate vertical in the EU's regulated jurisdictions while it stays open, for now, in parts of the US. The legal ground under those US markets is itself contested, seen in the college-marketing lawsuit against Polymarket in Washington. Nevada, separately, is pushing to hold Kalshi in contempt over geofencing after investigators bought banned contracts from inside the state. What is next in the Netherlands is a possible further appeal by Adventure One to the courts, and, given the June 18 pact, more coordinated action from the other eight regulators that just put their names to the same position.