Not aware of any aviation or airline legislation i.e. FAA, ICAO, IATA regarding transportation of criminals. Besides, some people can be considered criminals in one jurisdiction, and not in others... Yes, a few times I had prisoners on board, escorted by police... and also had people deported from a country back to their country of origin... some also escorted by police.
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As far as I am concerned, it is a legal problem which could be imposed on any given airline in any given country, but as pilot, I had enough other aviation rules to observe and be concerned about, to further worry about this.
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Happy contrails