I expect Nick Freeman might be touting for business at the judicial review stage, which I would very much like to see. The secretary of state may well have signed a piece of paper that says a sign with the five* words "Ultra low emission ULEZ zone" conveys the existence of a charge and directs motorists to the TFL website, but that doesn't make it true.
Given the camera authorisation fiasco, I wouldn't be too surprised if TfL had actually forgotten to get the LEZ ones authorised.
*Or four, if you take into account the fact that ULEZ isn't actually a word**
** Unless you're Macedonian, in which case it is a word which translates to 'Get in' or Finnish in which case it translates to 'Get out'... which doesn't help much.