Good question - I don't know. Many countries do not allow passports to be mailed, or carried by someone else, over international borders. My question to you would be, why are you asking? If the problem is that the husband is not eligible to enter the US to submit the passport himself, there are usually instructions included with the request for the passport about how to mail the passport to a location in Fort Erie, Ontario, to get the C.O.P.R. When it's received back, the husband could make an appointment with his local CIC office for his landing interview - even though he is an outland PR applicant.