Pirate attacks in the waters off the Horn of Africa, including those on U.S.-flagged vessels, have brought continued U.S. and international attention to the long-standing problem of piracy in the region. A recent development in one of the piracy trials in Norfolk, VA, has highlighted a potential limitation in the definition of piracy under the United States Code. This report first examines the historical development of the offense of piracy, as defined by Congress and codified in the United States Code. The focus then turns to how contemporary international agreements define piracy. Finally, the report highlights a recent federal district court ruling that the offense of piracy under 18 U.S.C. § 1651 requires a robbery at sea.