I would use CanCan ability.rb file for that: https://github.com/CanCanCommunity/cancancan
It's already a file where you just throw in all of your authorization logic anyways so it always feels a bit unruly once you get beyond basics.
I love the idea of Pundit because it decouples all that as much as seems practical. I'm about to find out if theory informs practice or not...