https://www.swissinfo.ch/ger/auslieferungs-gesuch/2803478
Argentina asked Switzerland to extradite Jean Bernard Lasnaud for smuggling Weapons to Ecuador and Croatia (he's French), and why Argentinia? Because the former President Carlos Menem and other Politicians where involved in it.
As an example, France would ask A if he can extradited to France and prosecuted there, even when let's say the crime was in Country B. The US did something like that with Otto Warmbier:
https://en.wikipedia.org/wiki/Otto_Warmbier
That whole thing is often not National or International Law but Diplomatic (especially with someone like Assange)