I think from his side it's a weak argument to follow but maybe it makes sense in a common law context - whatever instance has given him a go-ahead, he's going to use that and say he had some kind of assurance. It's just not from the right department or level at all, but he can try. He needs a pseudo good faith argument for "I thought I could go", and that's what he's trying to do - that's his foot in the door, then the courts decide.