Yeah I think that's a pretty common thing to do. Outside of US and some EU countries, I know Carlos Ghosn is famously hiding in Lebanon where he is a citizen.
You’re right, every treaty is a different beast and there are no absolutes. But the general principle is Further, 18 U.S.C. 3181 and 3184 permit the United States to extradite, without regard to the existence of a treaty, persons (other than citizens, nationals or permanent residents of the United States), who have committed crimes of violence against nationals of the United States in foreign countries.
If the applicable treaty or convention does not obligate the United States to extradite its citizens to a foreign country, the Secretary of State may, nevertheless, order the surrender to that country of a United States citizen whose extradition has been requested by that country if the other requirements of that treaty or convention are met.
Those seem to be the mechanisms to extradite in the absence of a treaty. No point in having laws about treaties because ratified treaties trump the law (is my understanding).
