IIRC correctly the CF Dress amendments brought out by the CF Dress Committee chaired by CF CWO states:
Men: Hair shall taper-trimmed at the back. Style and colour shall not present a bizarre, exaggerated, or unusual appearance. Sideburns shall not extend below a line horizontally bisecting the ear. Moustaches shall be kept neatly trimmed.
Women: Hair shall not extend below the lower edge of the shirt collar. Braid, if worn, shall be styled conservatively and tied tightly.
The bold, underlining of the words are mine. These adjectives permit each RSM to define a standard for their soldiers. At a Unit, Base or HQ where the RSM looks great with a Marine-style haircut, then it becomes the standard. If he does not then it could be seen as unusual or bizarre. The interpretation of dress regulations should be left to the chain of command and not the individual.
This policy in its many previous forms has been challenged via the CF Grievance Board and the Cdn Human Rights Tribunal. The result of these challenges is the carefully chosen adjectives stated above for both Men and Women.