Extradition looks in headlines like a transfer between police forces. In practice it is a layered legal process in which courts and the executive branch each hold a separate veto.
A treaty sets the boundaries
Most extraditions run under a bilateral treaty that lists which offenses qualify and what evidence a requesting country must supply. Without a treaty, cooperation is discretionary and often refused.
A common requirement is dual criminality: the conduct must be an offense in both countries. Conduct that is criminal in only one of them generally falls outside the agreement.
Treaties also carry exceptions, typically for political offenses, and sometimes bar surrender of a country's own nationals, which is why some states prosecute at home instead.
The request travels through diplomatic channels
A prosecutor cannot simply ask a foreign counterpart. The request is assembled with supporting documents, certified, translated and passed through the central authorities of both governments.
Because a fugitive may move before that paperwork is complete, treaties usually allow a provisional arrest request first, holding the person while the full package is prepared.
Those holds run on a clock. If the complete request does not arrive within the period the treaty allows, the person can be released even though the case continues.
A court reviews it before anyone moves
The receiving country's court does not retry the underlying case. It asks a narrower question: whether the treaty conditions are met and the evidence clears the threshold the treaty sets.
Defense arguments are shaped by that limit. They tend to focus on identity, whether the offense is covered, elapsed time, and whether the person would face treatment the receiving country cannot accept.
Appeals are available, and each level adds months. A contested case moving through the full appellate path can occupy several years before any decision becomes final.
The final step is political, not judicial
A court ruling that extradition is permissible does not by itself move anyone. In many systems a minister or secretary makes the surrender decision after the judicial stage closes.
That official can weigh factors a court did not, including health, humanitarian concerns and assurances offered by the requesting state about how the person will be treated or sentenced.
Assurances are a common condition. A country that will not surrender someone to face a particular penalty may agree once the requesting government commits in writing that the penalty will not apply.
Why alternatives get used instead
Because formal extradition is slow, governments sometimes rely on immigration law, deporting or refusing entry to someone who is removable on other grounds.
Those routes are faster but legally distinct, and they attract criticism when they appear to substitute for a process that carries more safeguards.
Specifics vary considerably by jurisdiction and change as treaties are renegotiated, so any individual case turns on the particular agreement in force between the two countries involved.