Its either one or the other for specific areas. For example the EU has their own policy on flight time regulations (EASA) and the CAA have theirs (CAP371). Under EU policy all member states will have one set standard to follow however if left nationally, the CAA will dictate what is safe and what is not. I don't trust what comes out of Brussels, but I do trust the CAA as they have the UK Aviation as their core interest. Also pointing out that the UK has higher standards, look at what BALPA have said about this issue