BetVIP, credited with being the first fully licensed bitcoin sportsbook, enables users to place bets with the digital currency.
Daniel Schwartzkopff, CEO of BetVIP, said Coinbase had previously confirmed in writing that it would act as a bitcoin payment processor for the all-purpose betting platform.
A spokesperson for BetVIP claimed Coinbase now prohibits all gambling, whereas before it only prohibited illegal gambling operations.
Nick Tomaino, business development manager at Coinbase, said he was unable to comment on specific accounts, but countered the spokesperson's claims.
He confirmed Coinbase wallets and APIs "are open to use for anyone in the world that operates legally, and the same holds true for gambling businesses", adding:
"We do have to be sure that we are fully compliant, though, so we can continue our mission of making bitcoin easy to use for consumers, merchants, and developers around the world," he said.
Schwartzkopff said BetVIP's aim was to bring "transparency and legitimacy" to a sector that had been "marred with controversy and fly-by-night operators". He added that BetVIP provided this, and more, with a public management structure and an eGaming license from the Caribbean island of Curaçao.
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