France Blocks Polymarket After Weather Sensor Probe

France Orders ISPs to Block Polymarket After Suspected Weather-Bet Manipulation

France has ordered internet service providers to block access to Polymarket, escalating its response to a prediction-market platform it considers an illegal gambling service.

The decision followed allegations that a weather sensor near Paris Charles de Gaulle Airport may have been tampered with to influence bets. While the investigation has not established who was responsible, the incident exposed a difficult question for regulators: what happens when online wagers create an incentive to alter the real-world data used to settle them?

A $119 Bet That Raised Serious Questions

In April 2026, a temperature sensor at Charles de Gaulle Airport recorded an unusual late-evening spike. The reading reportedly jumped from around 16°C to 22°C, despite no comparable movement at nearby stations.

An anonymous Polymarket trader had placed $119 on the outcome shortly before the spike. The account later made more than $21,000 in profit and then deleted its username. French weather service Météo-France filed a complaint after detecting suspicious sensor data and physical findings on one of its instruments. The police investigation is ongoing.

The key point is that manipulation remains an allegation, not a proven fact. However, the case showed how even a small, accessible data source can become a potential target when it determines the result of a high-value online market.

Why France Moved From Payment Restrictions to a Nationwide Block

France’s National Gambling Authority (ANJ) had already acted against Polymarket before the weather controversy. Its latest decision reflects the regulator’s view that earlier measures did not stop French users from accessing the platform.

1. November 2024: Financial Transactions Were Geoblocked

After an initial formal notice from the ANJ, Polymarket implemented measures intended to prevent financial transactions related to its gaming products from French territory. The platform itself, however, remained visible online, allowing people to follow markets and real-time odds. ANJ says those restrictions were circumvented in practice.

2. February 2026: Prediction Markets Were Declared Illegal Gambling

In February, ANJ reiterated that prediction-market platforms were not authorised in France and should be treated as illegal gambling services.

The regulator argued that these platforms can share the addictive features of online gambling while lacking safeguards expected in regulated markets, such as effective identity checks, spending controls, and self-exclusion tools.

3. April 2026: The Weather-Sensor Case Triggered a Criminal Inquiry

The Paris weather bets made the risks more concrete. Météo-France said it had filed a complaint for suspected interference with an automated data-processing system.

Polymarket subsequently switched the reference station for Paris temperature bets from Charles de Gaulle Airport to Paris-Le Bourget Airport. Reports on the case noted that the Charles de Gaulle sensor had been used to settle the contracts.

4. June 2026: French Traffic Continued to Rise

According to ANJ, Polymarket recorded 578,751 visits from France in June, involving 205,057 unique visitors. Those figures persuaded the regulator that payment restrictions alone were not preventing exposure to the platform.

5. July 16, 2026: ISPs Were Ordered to Block Polymarket

On July 16, the president of ANJ ordered French internet service providers to block Polymarket. The regulator announced the decision publicly the following day.

ANJ said Polymarket’s homepage, with continuously updated odds, promoted an unauthorised gambling offering. It also noted concerns about potentially manipulated bets and inadequate user verification. Reuters reported that Polymarket did not immediately respond to requests for comment.

Why the Homepage Became Part of the Regulatory Case

The French action is not only about placing a wager. It is also about visibility.

ANJ considers the display of live odds to be a form of promotion for an unlicensed gambling product. Under French law, advertising unauthorised gambling services can carry a fine of up to €100,000.

This approach matters because platforms do not need to complete a transaction to attract users. Real-time probabilities, market charts, and headlines can keep people engaged long before they try to deposit funds.

Can ISP Blocking Actually Work?

An ISP block can reduce casual access and send a strong regulatory signal. It is especially effective at making an unlicensed service less visible to everyday users.

However, it is not a complete solution. Location-masking tools can sometimes weaken internet-level restrictions, while borderless platforms can serve users across many jurisdictions. That means enforcement cannot rely on blocking alone.

The Larger Challenge for Regulators

The Polymarket case highlights three broader issues:

• Consumer protection: Prediction markets may not offer the same harm-reduction tools required of licensed gambling operators.
• Market integrity: Participants may be tempted to use inside information or influence the underlying event or data source.
• Cross-border enforcement: A platform can operate globally while national regulators have authority only within their own borders.

France’s decision is therefore likely to be watched closely across Europe. Other countries may consider similar measures, particularly where prediction markets are treated as gambling rather than financial products.

The Bottom Line

France’s block of Polymarket is a warning that regulators are no longer viewing prediction markets as a niche crypto product. The suspected weather-sensor manipulation case transformed an abstract compliance dispute into a tangible public-interest concern.

Blocking a website may limit access, but the real test will be whether regulators can combine technical restrictions with clear licensing rules, effective identity checks, consumer safeguards, and stronger market-integrity standards.