This piece was originally submitted in November 2012 in satisfaction of the Australian National University College of Law's Honours program. The dissertation identifies uncertainty in the Article 101 UNCLOS definition of maritime piracy as an obstacle to the effective prosecution of piracy offences at the domestic level. After surveying relevant domestic decisions and legislation purporting to give effect to the customary and/or conventional definition of piracy (as evidence of State practice and opinio juris or subsequent practice relevant under Article 31(3)(b) VCLT) the dissertation adapts the approach of the International Criminal Court of establishing 'elements of crime' for Rome Statute offences, and attempts to articulate such elements of crime for maritime piracy.