OK I get this part. I came back 3 times from Mexico this year and only last time they insisted for a pr card even though I told them I wasn't pr yet. In this case, how the company can refuse only the RTD if they don't have access to Canada immigration system to know if the person is also a pr or not. And arriving in Canada they can't deny her entry with RTD only, anyways.I think the person will need to provide document such as PR card, PRTD, ETA, visa and etc. before boarded. Also, Canuck only mentioned "air". I suppose someone also cross international borders through marine vessels.
