Originally Posted by
bocastephen
Which is especially stupid when they do this at pre-clearance departure points where you've just cleared US immigration

If the doc check is at pre-clearance terminal during boarding, the airline is complying with transport canada regulation that all passengers present id to the gate agent. However, at the gate, any govt issued id is sufficient, so you can give the agent your Hawaii or Arizona drivers license and it is acceptable as passport.
The Canadian gate agent doc check is equivalent to the TSA doc check in the USA.