South Korean authorities are investigating the country’s third-largest cryptocurrency exchange for allegedly providing a “gambling service.”

On Wednesday, the Korea JoongAng Daily reported that the Gyeonggi Nambu Provincial Police Agency had launched a probe into the Coinone exchange’s margin trading scheme, in which customers could effectively wager on whether the price of a cryptocurrency would rise or fall.

The police claim that margin trading is gambling by another name due to customers risking money on an outcome determined by chance. Coinone disputes this interpretation, noting that short-selling is common on Korea’s traditional stock exchange platforms, but the police insist that crypto exchanges don’t rise to the same standards.

South Korea keeps an extremely tight lid on its citizens’ ability to gamble. Local residents are allowed to gamble at exactly one of the country’s land-based casinos, and the only other legal options include the lottery, plus limited forms of sports and race wagering.