Mohammad Saaili Shibin is charged with piracy, kidnapping and weapons charges for his role in the hijacking of a yacht off the coast of Africa that left all four Americans onboard dead.

Prosecutors say Shibin never boarded the yacht Quest, but operated from land in Somalia to determine how much money the hostages could be ransomed for once they were brought to Somalia. Shibin attorney James Broccoletti wrote in a court filing Monday that merely communicating with those who boarded the Quest doesn’t constitute piracy.

“This count should be dismissed because under no set of facts was the offense of ‘piracy’ committed,” he wrote.

The government hasn’t filed a response yet and the US Attorney’s Office declined to comment on Tuesday.

This is the third case in which the definition of piracy has come under scrutiny. Exactly what constitutes piracy is currently being contested in a federal appeals court in two other cases involving attacks on the USS Nicholas and the USS Ashland.

The US statute mandating a life sentence for piracy states that piracy is defined by “the law of nations” and was written in 1819.

Attorneys for Somali men in those cases contend piracy never occurred because they never boarded either ship. The government contends that the US definition of piracy is based on an evolving international definition that is different now than when the US law was written.

Broccoletti wrote that using an evolving international law to define piracy is inappropriate and isn’t what Congress intended. But if the court disagrees, he says the charge should still be thrown out because international law is too vague.

“Due process prohibits the imposition of criminal sanctions based on an uncertain criminal standard,” he wrote. “An evolving standard of criminal liability would be based on customary international law, which is, in this day and age, unable to be determined with certainty.”

He also said Shibin shouldn’t face piracy charges because he wasn’t contacted by the pirates until they had already taken control of the Quest.

The owners of the Quest, Jean and Scott Adam, along with friends Bob Riggle and Phyllis Macay, were shot to death several days after their boat was boarded.

They were the first US citizens killed in a wave of pirate attacks that have plagued the Indian Ocean in recent years, despite an international flotilla of warships that patrol the area.

Negotiations with the US Navy were underway when shots were fired aboard the Quest. Eleven men in the case have pleaded guilty to piracy. Three others are facing murder charges.