When the Russian commandos began rappelling from helicopters onto the Arctic Sunrise, Captain Peter Wilcox was exercising on an elliptical machine. The raid took place on September 19, as the Greenpeace boat was returning from placing a protest banner on a Russian oil rig in the Arctic. At first, the crew thought that being taken over by the Russians would help with the publicity of their cause. Captain Wilcox had been with Greenpeace for forty years and he assumed the boarding was just “part of the game” played between states and activists.

When the boat was taken to the Russian port city of Murmansk, though, they were confronted with a different reality: Prosecutors were charging the crew with piracy, a charge that carries up to fifteen years in prison. After a brutal transport aboard a prisoner train car, the activists were released on bail last week, the charge reduced to “hooliganism.”

Though the piracy charge was dismissed, the episode raised an interesting question in international law; who exactly is a pirate? As it turns out, it’s not just Vladimir Putin who is taking an expansive view of the term.

Traditionally, piracy was carried out as a form of robbery to enrich the pirates. In the ‘golden age’ of piracy, pirates such as Blackbeard commanded large fleets of ships and amassed huge fortunes on the high seas. The pirate crews also profited from the raids and there were even systems of workman’s compensation for the crews.

Under international law, piracy prosecutions traditionally required that the alleged pirates were seeking private gains. The Harvard Draft Convention on Piracy from 1932 noted that, “If an attack by a ship manned by insurgents is inspired by a motive of private plunder, it may be piracy under the definitions of the draft convention.” Under the United Nations Convention on the Law of the Sea, piracy requires the use of violence against a ship when it is “committed for private ends.” The requirement fits with the traditional definition of a pirate as a businessman seeking to enrich himself and his crew. In the 1820 case of United States v. Smith, the U.S. Supreme Court defined piracy as “robbery on the high seas.”