If you cannot "really enforce" one policy why do you think you will be able to "really enforce" the other?
When enforcement doesn't work rules are guidelines.
When enforcement doesn't work rules are guidelines.
As I said, you start by creating a culture where rules are enforced, then work from there.
Sunday is free because it is 'overtime'. Workers are paid fixed pay per month. Suing for Sunday would not bring any extra money to worker.