[Quarrel]

This is not true. Like, (almost) at all. (There are a few tiny exceptions, for instance, if an EU national commits child sexual abuse overseas, they can be prosecuted for it in the EU)

Two Germans shooting each other in Australia break Australian law, but not German law.

[chopin]

Germany does in fact prosecute severe crimes done in foreign countries. It will not act if Australia does, but it will act if Australia doesn't.