Some of the issues that arose in the context of Israel trying Eichmann was whether Israel was right to forcibly remove Eichmann from Argentina and try for human rights issues that he committed before the statute under which he was tried was enacted. Also could Israel try Eichmann given that the offense was committed outside Israel on people who were nations of Israel. Now F.A Mann answers for these questions stating that the nature of the crime made it clear that Israel could indeed try Eichmann, and that the nature of the crime alone is enough condition albeit an international statute or a treaty. Applying this to our understanding of the Universal jurisdiction, nation states can carry out criminal proceedings based on the nature of the crime alone.
Therefore, based on the nature of the crime, international law allowed Universal jurisdictions for states over its own and other state nationals. Some of the states that have applied universal jurisdiction principles are as follows:
In the year 1985, the United States authorized the extradition of an individual who was alleged as a war criminal. He was alleged to have committed crime that could be called genocide. The nature of the crime hence means that the United States could have him extradited according to their jurisdiction to a country that made the allegation.
The fundamental nature of the Universal jurisdiction was accepted in the Barbie case where by reason of their nature, although the French municipal law could not indict the person, the international criminal order meant that they could implement extradition rules even if it was foreign to their own system
In the case of the Canadian courts, a notable case was where a non-Canadian was accused of war crimes. He committed these war crimes in WW2. And the person was a non-Canadian citizen, however, given the nature of the crime and the Universal jurisdiction principles, Canadian courts implemented criminal proceedings for the crime.