Wikipedia: Nullum crimen, nulla poena sine praevia lege poenali/Talk

: This basic legal principle has been incorporated into [international criminal law].

No it hasn't. ICL relies on breaking this rule.

: penal law is taken to include the prohibitions of international criminal law, not only those of domestic law.

If some ICL isn't ratified by the country, it isn't a law there.

Article should be made NPOV. --Taw

International criminal law has explicitly incorporated nullum crimen. See, e.g. the Rome Statute of the International Criminal Court, article 22, which is titled "Nullum crimen sine lege" and which provides:

A person shall not be criminally responsible under this Statute unless the conduct in question constitutes, at the time it takes place, a crime within the jurisdiction of the Court

And article 23, entitled "Nulla poena sine lege", which provides:

: A person convicted by the Court may be punished only in accordance with this Statute.

You also say:

: If some ICL isn't ratified by the country, it isn't a law there.

There are two ways international law can be created: by treaty, or by custom. You are correct in regards to international law created by treaty, but much of international criminal law is customary. Customary law does not require any formal act, such as a ratification, to come into effect. Crimes such as genocide are customary international law, and are illegal in all states even if that state has not ratified the treaties explicitly making it so.

The majority of legal opinion holds that international criminal law does not violate nullum crimen in any way. The article is NPOV. -- SJK

In almost all courts on this planet you can't do any legal action on basis of "customary international law". This clearly shows that "customary international law" is not a law in traditional meaning, and ICL either (interpretation issue) breaks "Nullum crimen..." or changes definition of law. --Taw

Taw: That is absolutely false. Just about every court on this planet accepts the existence of customary international law, and will refer to it on occasion. The problem is not that they don't recognize customary international law, it is that the cases in which domestic cases permit any sort of international law to be applied are limited. International courts and arbital tribunals (the ICJ, ITLOS, ICTY, ICTR, PCA) are quite willing to apply it, provided they have jurisdiction.

Customary international law has been recognized as law, at least in the West, since the 17th century or earlier (see e.g. the works of Grotius) . So if its not law within your meaning, your meaning is not the traditional one. -- SJK