I know this is of little interest to most folks, but to the subcommunity it affects, it could be a significant change in being able to fly commercially.
The current Canadian Identity Screening Regulations have been written so that a person who doesn't a) doesn't resemble the photograph b) does not appear to be the age on the document c) doesn't appear to be the gender indicated on the document
shall not be transported.
http://laws.justice.gc.ca/eng/regula.../FullText.html
5.2 (1) An air carrier shall not transport a passenger if
(a) the passenger presents a piece of photo identification and does not resemble the photograph;
(b) the passenger does not appear to be the age indicated by the date of birth on the identification he or she presents;
(c) the passenger does not appear to be of the gender indicated on the identification he or she presents; or
(d) the passenger presents more than one form of identification and there is a major discrepancy between those forms of identification.
(2) Despite paragraph (1)(a), an air carrier may transport a passenger who presents a piece of photo identification but does not resemble the photograph if
(a) the passenger’s appearance changed for medical reasons after the photograph was taken and the passenger presents the air carrier with a document signed by a health care professional and attesting to that fact; or
(b) the passengers’s face is bandaged for medical reasons and the passenger presents the air carrier with a document signed by a health care professional and attesting to that fact.
So, if you're a person who has transitioned to the other gender, and can't get the gender marker changed on your documentation, you're not going to fly in Canada. Fortunately the US Department of State makes it fairly easy to change the gender marker on a passport, but not all countries (including Canada) make that possible without surgery.