The Klaestron-Federation Extradition Treaty was a treaty that as of 2369 regulated extradition of Federation citizens who had committed crimes on Klaestron IV to the Klaestron government. Apparently, it was only applicable to people residing in Federation space.
In 2369 Ilon Tandro tried to invoke the treaty to return Jadzia Dax to Klaestron IV, though this proved difficult as she was currently residing on Deep Space 9, in Bajoran space. (DS9: "Dax")
Since Dax was facing a possible death penalty, the treaty apparently did not have a clause denying extradition in such cases, as is often the case in modern-day countries opposed to the practice; although the Federation still seems to have a legal concept of death penalty in the 24th century, it is virtually abandoned in practice.