They can't provide a definitive list because case law can always overturn it.
I guess the best they can offer is "if you do this, we will choose not to go after you". But even that can change, as you point out. They don't have the resouces to chase even close to everyone, so they have to rely on media messaging to do a lot of the policing for them (hence going after high-profile targets like TV presenters).
I guess the best they can offer is "if you do this, we will choose not to go after you". But even that can change, as you point out. They don't have the resouces to chase even close to everyone, so they have to rely on media messaging to do a lot of the policing for them (hence going after high-profile targets like TV presenters).