There's always the caveat for 'safety/operational reasons, though, isn't there?
http://www.cmp-cpm.forces.gc.ca/dhh-dhp/pub/ins-265/index-eng.asp
Example:
CHAPTER 2 - POLICY AND APPEARANCE, SECTION 2 - APPEARANCE
HAIR
4.Hair on the head shall be neatly groomed and conservatively styled. The length, bulk or style of hair shallnot detract from a positive military appearance or preclude the proper wear of military headdress. (Bulk is the distance that the mass of hair extends from the skin, when groomed, as opposed to the length of hair.) In particular, style and colour shall not present a bizarre, exaggerated, or unusual appearance. Unusual colours, such as green, bright red, orange, purple, etc., are not permitted. Hair must be secured or styled back to reveal the face, and any accessories used to secure or control hair styles shall be as unobtrusive as possible. Hair ornaments shall not be worn, except women’s conservative barrettes which blend with the hair colour. Shaving of all of the hair on the head is permitted. The personal manner of wearing hair within these general style limits, including moustaches, beards and braids, shall be modified to the degree necessary to accommodate operational or occupational equipment, such as gas, oxygen and scuba masks, hard, combat and flying helmets, etc., where a member’s safety or mission is put in jeopardy.
And, stepping back - there is this para as well.
CHAPTER 1 -COMMAND, CONTROL AND STAFF DUTIES
8.Control is exercised by local commanders who may standardize the dress of subordinates on any occasion, including the wear of accoutrements and alternative or optional items, subject to overall command direction.
Earrings are permitted now for females, but let's say a JTF commander thought there was a reason people should not be permitted to wear earrings ever while on that deployment. Well, that gets approved and put into the theatre dress instructions. Or, how on my Wing, regardless of if you're on the flight line or not, your reflective strips on the rain jacket shall be visible. I bet that wouldn't go over in Pet.
My line of work, women can wear earrings flying, and have long hair - they also have to be able, for safety and mission reasons, be able to wear a few different masks and a flying helmet. If they can do that with long hair and earrings...I can't see an valid argument for safety/mission reasons against males being able to wear long hair or earrings during flying ops.
* that's not to say whether I agree, or disagree with the possible changes. My job is to support and enforce, not determine policy.