There will always be exceptions to the rule. Until you eliminate them. If you can.

As we enter into negotiations I want you to think about the things that go against the collective agreement. Could be a rule you bend, or the corporation ignores. A stipulation that alone doesn't really change anything but collectively could cause harm down the road. Eventually it is found out and either stopped immediately or it gets a discussion. Based on how widely successful it is or how detrimental it could be if other knew it existed. Sometimes it just sits there quietly not hurting anyone.