There are both gaps and weaknesses in the various sources of International Criminal Law in norms and enforcement modalities. A comprehensive international codification would solve these problems, but this is not forthcoming.
M. Cherif Bassiouni,
International Crimes: Jus Cogens and Obligatio Erga Omnes,
59 Law and Contemporary Problems
Available at: http://scholarship.law.duke.edu/lcp/vol59/iss4/6