As l9ng as it is the same, there is no excess compensation, so they are not mercenaries - even if they make more money there than someone that meet all th3 criteria of a mercenary in a poor nation.
If in individual is brought to a court in a country using common law, it would make sense they use that principle to try to make sense out of the law.
Right now, the Wagners are in Ukraine, Are they really residents of Ukraine if they come from Georgia? They could be on a plane to an African nation the next day.
In a situation where Wagner group fight alongside their Russian military, you don’t call them mercenaries. They are Russians. Same way you called Azov battalions Ukraine forces, that same way you should refer to Wagner as Russian forces.
It's the same, US Military do takes non-American, and they have the same paygrade than American Citizens, it was paid to soldier according to rank and not according to the Citizenship status.
Again, first of all, International Law is not common law. In fact, as my wife said, international law is a different jurisprudence all together because you would have to fit that into all kind of legal system in the world, at least to the framework for those who sign those law and treaty.
On the other hand, a lot of international treaty does not actually make sense. That's why most international law tends to update over time.
They’re (Wagner) state owned anyway ( Russian)