"Bitcoins are funds within the plain meaning of that term," Nathan wrote. "Bitcoins can be accepted as a payment for goods and services or bought directly from an exchange with a bank account. They therefore function as pecuniary resources and are used as a medium of exchange and a means of payment."
The decision did not address six other criminal counts that Murgio faces, Nathan wrote.
Brian Klein, a lawyer for Murgio, said he disagreed with the decision.
"Anthony Murgio maintains his innocence and looks forward to clearing his name at his upcoming trial," he added.
Prosecutors last year charged Murgio over the operation of Coin.mx, and in April charged his father Michael with participating in bribery aimed at supporting it.
Authorities have said Coin.mx was owned by Gery Shalon, an Israeli man who, along with two others, was charged with running a sprawling computer hacking and fraud scheme targeting a dozen companies, including JPMorgan, and exposing personal data of more than 100 million people.
That alleged scheme generated hundreds of millions of dollars of profit through pumping up stock prices, online casinos, money laundering and other illegal activity, prosecutors have said.
Shalon has pleaded not guilty, and is being held at the Metropolitan Correctional Center in Manhattan. He hired new lawyers last month and is seeking permission to replace lawyers who joined the case in June, a Monday court filing showed.
The case is U.S. v Murgio et al, U.S. District Court, Southern District of New York, No. 15-cr-00769.
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