And then she even said that even if the regulator did have statutory authority, she wasn't sufficiently convinced.
Which is to the opposite side of the spectrum... "even if you have the authority, I can just say "I'm not convinced by the argument that you don't owe me, so I'll still block it"."
There are plenty of cases where executive authority may not be enacted in an arbitrary manner. The government probably spent more time asserting that they had the authority to do so, than that doing so was necessary.
Either way, this will likely end up in a different court, and at a higher level, and get decided again.
Which is to the opposite side of the spectrum... "even if you have the authority, I can just say "I'm not convinced by the argument that you don't owe me, so I'll still block it"."