International law for dummies

12 To prove a principle of customary international law, an international lawyer might look to diplomatic correspondence, opinions of government legal advisors, international organization reports, and reports of State behavior, among other written evidence.
Id. at 19.

The reality there looks quite different.
The world has no global police force or international prison.
If a country doesn’t like a certain law, it can simply choose not to follow that law.
That makes holding countries accountable for their actions quite difficult.

To understand international criminal law, it is first important to understand its components

First, international law rules over the relationships between and responsibilities of interacting countries

Next, criminal law establishes what is and is not considered a crime, and then sets up respective punishments for those crimes