A robust trade in digital ‘skins’ has helped the game’s popularity surge—Buy CS GO Skins and abetted wagering.

  On Thursday, a player named Michael John McLeod filed suit against Valve Software, accusing the game maker of enabling and indirectly profiting from illegal gambling surrounding its game Counter-Strike: Global Offensive. The gambling operations allow digital ‘skins’ for in-game weapons to be bet on the outcome of matches in the competitive game.

  That lets U.S. gamblers circumvent bans on online betting, but the skins can be easily bought and sold for real money, allowing them to act something like chips. Bloomberg has reported that the total value of such gambling is as much as $2.3 billion.

  Get Data Sheet, Fortune’s technology newsletter.

  It’s all possible because Valve, according to Polygon, allows third-party sites to easily link to player accounts on its Steam service, where skins are bought and sold. That has enabled the growth of gambling and marketplace sites with names like CSGO Lounge, CSGO Diamonds, and OPSKins. A CSGO representative told Bloomberg that Valve employees had directly communicated with the site and even offered technical support.

  Perhaps most troubling is the fact that many of these sites require no age verification, and the suit claims McLeod lost money gambling both as a minor and as an adult. The suit further alleges that “most of the people in the CS:GO gambling economy are teenagers and under 21.”

  Valve makes a transaction fee of 10% on CS:GO items bought and sold on its Steam marketplace, where certain weapon appearances can change hands for hundreds of dollars. But the practice has also impacted the popularity of the game itself. According to Bloomberg, CS:GO got off to a weak start, but the playerbase exploded after the introduction of skins and, with them, gambling.

  “In sum, Valve owns the league, sells the casino chips, and receives a piece of the casino’s income stream through foreign websites,” reads the suit in part. It characterizes the idea that Valve is not benefiting from buy csgo skins with paypal or directly involved in gambling as a “charade.”