In order for "it" to go to court, "it" has to be a cause of action recognised in law.
A regulator changing its mind is not, of itself, a cause of action recognised in law.
A regulator being incompetent is not, of itself, a cause of action recognised in law.
A regulator being stupid is not, of itself, a cause of action recognised in law.
A regulator being an arsehole is not, of itself, a cause of action recognised in law.
A regulator being a pompous prick is not, of itself, a cause of action recognised in law.
What you have to do, for example, is apply for a certificate and have it refused by the regulator, then seek judicial or merits review of that refusal. The refusal by a regulator to grant you something you've applied for and the regulator can grant you is a cause of action recognised by law. It may well be that in the course of the review some relevant matter about the lawfullness and the merits of the regulator's decision arises as a consequence of the regulator being incompetent, stupid, an arsehole or a pompous prick.
As another example, someone may have reasonably relied, to their detriment, on representations made on behalf of a regulator. Someone may make very important and expensive business decisions on the basis of representations by a regulator - which representations may include silence when the regulator should have said something - to the effect that the person's arrangements were in compliance with the law and would be certified. If it turns out the regulator led the person down an expensive 'garden path', the person may have an action in negligent misstatement. It is here that the prevaricators, the incompetents, the stupid, the arseholes and the pompous pricks occasionally get regulators into trouble.
Purely hypothetically of course.