I don't mean extradition in the common sense where the Government agrees to capture a resident and send them over for trial, more, what happens if the foreign Government decides to come in for themselves, and pick up that person.
Hypothetical scenario: a billionaire buys up a load of land in Western Australia, or something, and sets up an ancap state. Early on, somebody from the USA moves over and "renounces" US Citizenship, refuses to pay US taxes (that they claim he "owes"). The US Gov't wishes to make an example of this person, and either hires out a company within the country to capture this person and bring him to them, or just sends the Marines in, or something like that.
I've watched Bob Murphy's stuff on private defence, and how cities could get a collective insurance which could win through asymetrical warfare... but this is a very specific case of a Government going in after one person.
It might seem like an extreme scenario, but it's something that could very likely occur with the creation of the Ancap society... after all, lots of people would move over there to avoid taxes, and the Governments of the world would try to discourage this as much as possible.
I personally would boycott and encourage others to boycott any company that assisted a foreign government in reclaiming their tax slaves. Presumably the standard for foreign criminals now on Ruritanian (the name I have given our hypothetical libertopia) soil would be a trial in a fair Ruritanian court (where of course victimless crimes like the heroic action of tax resistance would not be acknowledged). Efforts by foreign nationals to commit the actual offence of kidnapping would ideally be prevented by private defense agencies. Might be tough to get the kidnapped victim out of Ruritania, especially if the person knew they were @ high risk and funded a high level of protection for themself.
... just as the State
has no money of its own, so it has no power of its own - Albert Jay Nock
That scenario could occur within our current society and I think it might actually occur. Under the guise of Interpol and national court systems they can call for swat to come and collect you from another country if you owe taxes. Well they might not send a swat but they will definitely find you and ask for the money.
I think it would be simpler to deny him reentry until he agrees to pay his taxes.