I remember a story about a BA flight from India? that was 'delayed' 14hrs. Reason? The crew were allocated a hotel for a stop-over where there was extensive renovation/building work going on. The crew needed to sleep during the day for an evening departure. They had no chance of sleep. Captain called delayed the flight until the next morning so the crew could have a proper sleep and be fit for the flight. This was a case of declaring yourself 'unfit to complete the duty'. It was incontestable and the root blame could be laid at the door of the employer. Slam-dunk. Good solid union airline. Well done.
Compare this to the call from a lowly non-union pilot that he could not sleep at home due to his neighbours having extension work done on their house, and could not sleep before an evening/night duty. One, the company accepts the excuse, the 2nd it is your fault for not managing your rest. It's a difficult world and you need to be opened eyed and aware before you dare enter.