Important Official Advice for Canadians
The Department of Foreign Affairs has recently given very detailed advice, including:
"Due to the heightened awareness of international child abduction, anyone, including parents, travelling abroad with a minor should be prepared to document legal custody of that child. Even when both parents are travelling with a child, they may be required to prove that they are the parents through, for example, presentation of the long-form birth certificate."
For children travelling with only one parent, DFAIT says, "[the] parent should have a legally certified letter of consent from the other parent or a custody document. In other cases, the individual with the child should have a legally certified letter of consent from both parents or a custody document."
And lastly, DFAIT continues: "When a minor child is travelling unaccompanied, parents should ensure that the child has a valid passport and a legally certified letter of consent for travel." A sample document can be found by following this link.
Other frequently asked questions are answered at the DFAIT website.