Campaigners, such as Jürgen Resch of environmental group Deutsche Umwelthilfe, have called the ruling "a great day for clean air in Germany." Experts believe high levels of nitrogen oxide (NOx), which frequently exceeds the EU threshold of 40 micrograms of NOx per cubic meter, causes between 6,000 and 13,000 deaths every year in the country,

The decision isn't being celebrated by everyone, though, as critics believe the rules will cause uncertainty for drivers and impact Germany's car market -- the largest in Europe. However, the government says there will be no immediate changes, and that it's considering a compensation scheme for those affected. It also stressed that the ruling was intended as guidance for individual cities. "It's really not about the entire country and all car owners," said Chancellor Angela Merkel.

The country has consistently led the charge on both car technology and sustainability, so if anywhere could successfully enforce policy like this it's Germany. The longer-term impact of this ruling won't be clear until more details on the legislation emerge, but it could set a strong precedent. With other countries already considering their existing vehicle policies, it might not be too long before they follow suit with similar decisive action.