When the FBI charged Ross William Ulbricht with running an illegal online drug marketplace, it waded into a nascent legal and regulatory struggle over the digital payment system called Bitcoin.

The government charged Ulbricht, a 29-year-old San Franciscan, with managing an online drug bazaar called the Silk Road under the pseudonym “the Dread Pirate Roberts” — a character in the 1987 movie “The Princess Bride.” Not only did the FBI say that Ulbricht profited from drug sales in his marketplace, but that he also twice tried to contract with Silk Road users to murder people he considered a threat to his anonymity.