playing devil's advocate re. your first point: surely there is info in the system, and it does not look like he is being detained in canada at this point, he is free to move about, but has been ordered to depart the country as a result of his offence. i guess a practical problem would have been, how can they identify him without id? it looks like they did eventually id him since he was let in and imprisoned for a few days, so they know who he is. at the same time the deportable offence remains: he presented himself at the border without an appropriate travel document.

re. your second point, i doubt a photocopy would help. it is not a valid travel document. it is something that might help you with people trying to (theoretically) help you, like your own embassy ("let me in, here's some evidence i'm one of your citizens"). his passport was not technically stolen if it was confiscated. besides, where would he report it stolen? he is in no man's land, there is no police station there.

i guess he could have refused to leave the usa side until they detain him or give him back his passport (which by the way is the property of the french republic).

al