Protect Our Parks has Richard Epstein representing them in the appeal.
Story from the Hyde Park Herald.
Epstein is a widely respected legal scholar, but I think his arguments here are rather weak. In the HPH story, he's just throwing all kinds of things at the wall, including questions of fact that an appellate court simply won't consider. Epstein had filed an amicus brief in the circuit court case with the curious argument that Mayor Emanuel, as Obama's former chief of staff, had a conflict of interest.