Answered by Shaykh Faraz Rabbani
Do muslim cab drivers refusing passengers who carry alcohol have a case?
Walaikum assalam wa rahmatullah,
In the Hanafi school, this is not from “assisting in sin,” because the service they themselves are providing–taking the customer from point A to point B–is permissible, as is the very act of allowing them to put “something” in the trunk. Please search SunniPath Answers (http://qa.sunnipath.com) for related answers on “assisting in sin.” [Ref: Ibn Abidin, Radd al-Muhtar]
If they are working for a cab company, then they would be religiously to follow company regulations on such matters, as these are part of their contractual agreement with their employer.
And Allah alone gives success.
Faraz Rabbani