In October 2007, a petition and public demonstrations were started, sponsored by private individuals with the backing of Alliance '90/The Greens and a variety of citizens' and environmental organisations. The aim was to collect 20,000 signatures and thus force politicians to take the issue to a local referendum. The petition gained 67,000 signatures but political wrangling began over whether the issue could be decided by a local referendum in the first place. Legal experts claimed that, as the project was not being financed solely from Stuttgart coffers, it was not for the city of Stuttgart to make the final decision.