This is not catered for by any IATA/ICAO rules.
Knowingly transporting a fugitive in order for them to evade/escape justice could amount to an offence under the law of the country in question, but there would have to be knowledge and intent on the part of the crew.
Possible offences in the UK might be assisting an offender or acts intended and tending to pervert the course of justice but would very much depend upon the facts of the case.
As an example, IIRC the pilot who flew Asil Nadir out the UK in a light aircraft shortly before his trial was convicted of perverting the course of justice. On the other hand the ferry company that transported a defendant I prosecuted last week to France the day before his trial would not have been aware of what he was doing and would not be prosecuted. [He was convicted of rape in his absence and sentenced to 13 years so I suppose its unlikely he'll be back in a hurry]