"Tirole's biggest finding is that the correct answer is, as the correct answer so often is in economics, “it depends”. We need to look at the details of that specific market and see how changing regulation and oversight would actually impact upon current behaviour, before we can decide what, if anything, should be done."
Since economics isn't a real empirical science no one can do that. You can estimate, predict or just guess, but you won't know until you try. You might then adjust the regulations if they aren't working as expected, but again you won't know the actual result of doing that until you actually do it. I'm not suggesting that all regulation is pointless, just that the basic premise of this particular argument is faulty.