Abdiwali Abdiqadir Muse was charged by the government with being the surviving pirate who kidnapped the captain and crew of the Maersk Alabama. off the coast of Somalia. He was charged with numerous counts including piracy. 18 USC 1851 which defines piracy is quite simple:

Whoever, on the high seas, commits the crime of piracy as defined
by the law of nations, and is afterwards brought into or found in
the United States, shall be imprisoned for life.

The statute was written in 1791 and it was last rewritten in 1948. Convicting Muse of piracy will be no easy trick. The statute’s simplicity will make it more difficult. Due process requires that a law give notice to those who would break the law as to what conduct will violate the law. The court will have to determine, “What is the law of nations?” In the process of answering this question it will have to answer the question, “Is the law of nations, clear enough to meet due process standards as to giving sufficient notice of the conduct it bans?” Are we talking about the law of nations as it existed in 1791, 1948 or the present? Does this in and of itself make it overly vague?

But as insurance the US Attorney has charged Muse with other offenses, which may be easier to understand and get convictions on including discharging a firearm, conspiring to commit hostage taking and brandishing a firearm