Because it's quite literally illegal in Canada since bill C-16 passed in 2017 not to allow them to play (discrimination), or to protest against them playing (hate crime). That's the result of self ID brought into law with no Equalities Act type exception clauses like in the UK.
You risk being charged with a crime yourself if you a coach, you a player, you a parent, you a spectator, dare say that this isn't fair or take steps to disallow it.
At best all you can do is refuse to play, quit the team, Canada really does need a lawsuit to sort this -- it will not be reversed or changed unless the Supreme Court rules the self ID law to be unlawful. I'm not holding my breath.