Demonstrators gather around Hambach Forest to protest deforestation in western Germany on Oct. 6. (Thomas Banneyer/EPA-EFE)

BERLIN — When 50,000 protesters headed to the ancient Hambach Forest west of Germany’s Cologne city last weekend, interest was so great that traffic on one of the country’s high-speed autobahns came to a standstill. While traffic jams aren’t normally something to celebrate, in this case the planned protest turned into a party after it was announced that a court had just temporarily blocked one of Europe’s powerful energy companies, RWE, from continuing to clear away one of Germany’s oldest forests to make space for a coal mine.

The rescue of the forest’s thousand-year-old trees was celebrated as a rare victory by environmental activists over European governments that have almost all ignored their own emissions targets in recent years. While support in European election campaigns this year for environmental parties has been on the rise from Sweden to Germany, it appears that there is another group forcing the governments to obey their own laws: judges.

Courts in Germany and other European Union countries are posing a growing challenge to governments and business interests in regard to climate change in recent months, as scientists have stepped up their warnings that the world has little time left to prevent a human-made global disaster.

On Tuesday, an appeals court in the Netherlands ordered officials to cut greenhouse gas emissions more rapidly than so far envisioned, handing a victory to 900 citizens who had sued the government. Last month, a German court banned all old diesel vehicles from the city center of Frankfurt, after Germany’s top administrative court had found earlier this year that the highly polluting cars could be restricted from accessing busy roads across the country. Similar decisions could follow, potentially Tuesday, when a Berlin court is expected to make a ruling on the same grounds.

Several other lawsuits are still being processed, including one by a group of litigants from France, Germany, Sweden and other countries who argue that the E.U.'s failure to force member states to dramatically cut greenhouse gas emissions violates the law.

Ironically, the E.U. itself is preparing to sue member states over their failure to cut emissions. Germany, for instance, vastly exceeds its targets, which may soon turn out to be a costly endeavor. When E.U. member states exceed their emissions targets, they can purchase the right to emit more from other countries that have not exhausted their limits. That way, the E.U wants to keep overall emissions limited and provide an incentive to countries to lower emissions themselves. Unless it dramatically changes course, Germany may have to pay $70 billion over the next decade to compensate for its additional emissions, according to some estimates.

The country’s problem is that despite its reputation for leading the way in promoting renewable energy sources, it continues to heavily rely on coal, one of the most polluting energy sources. Environmental researchers believe there’s no easy fix.

“It’s not just a technical shift. It’s a societal shift,” Rebecca Bertram, an energy expert with the Greens-party-aligned Heinrich Böll Foundation, told The Washington Post last year. “There are so many vested interests in keeping the old structures, and people will cling to them as long as they can.”

Germany’s prior commitments to reduce emissions also have faced a number of challenges, including the country’s decision to give up nuclear energy after the devastating 2011 Fukushima disaster and a lack of transport routes that would distribute renewable energy produced in northern Germany’s wind parks across the country.

But as courts are assuming a more influential role in regulating emissions, what may soon matter more than feasibility is legality.

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