The "excuse" is the Personenbeförderungsgesetz (law on [commercially] transporting people). Taxis have to implement it (and they do), and so they can complain i

The "excuse" is the Personenbeförderungsgesetz (law on [commercially] transporting people). Taxis have to implement it (and they do), and so they can complain in court about competitors who don't (as a remedy to state intervention: regulation has to apply to everyone). That's what happened here, nothing more, nothing less. If the court hadn't stopped Uber, we'd actually see some special treatment (that is, protectionism) in Uber's favor.