I am a single mom and have taken my son out of Canada 5 times - I have never had to show anything leaving Canada but twice returning - once at Calgary airport and once at Edmonton airport - they asked "where's his daddy?" I said, we are divorced, do you want to see the Sole Custody order - they said yes both times and read through it. I also have it in my divorce judgment that I have Sole Custody and that I can travel outside of Canada without the written permission of my ex. On the last trip when we arrived in Calgary, I told him that I appreciated him asking for the documentation but that I would rather be asked leaving the country because I would not want my ex to be able to take my son out. He said that they are mostly concerned that I am not bringing a child that doesn't belong in Canada in. I had always thought the letters were to safeguard our children from parental abductions but apparently not.