Poland must immediately stop extracting brown coal at a mine on the border with the Czech Republic and Germany, the European Court of Justice has ruled.
In March the Czech Republic filed for an injunction, saying the Turow open-cast lignite mine drains groundwater away from surrounding areas and is harming Czech citizens.
The court's ruling on Friday is a temporary measure pending its final decision on the complaint.
Poland is still heavily reliant on coal, which accounts for 48 per cent of Poland's energy production compared with less than 17 per cent from lignite.
State-run energy company PGE Group contested the claim, arguing it would take years to phase out black coal in line with EU climate policies.
Poland's climate minister Michal Kurtyka recently extended the mine's license until 2044. The country's new energy plan says the last black coal mine will be closed no later than 2049, but critics have called for it to end much sooner.
Planning to stick to coal mining beyond 2030 will mean the Polish region around Turow will miss out on a share of the EU's €17.5 billion "Just Transition" fund, which supports localities turning away from producing coal.
The court ruled that the previous 2026 license for Turow had infringed EU laws because it was granted without an environmental assessment.
Court vice president Rosario Silva de Lapuerta found that due to its "negative effects" the Turow mine must "immediately cease lignite extraction activities.”
The halt was welcomed by environmental campaigners. Kathrin Gutmann, campaign director for the Europe Beyond Coal group, said: “This ruling is a welcome reprieve for people living on the front line of this crisis, who have been forced to live with the mine gulping their drinking water and undercutting their houses."
“The message for polluters like PGE is clear: The rules are the same for everyone, and they are there to protect everyone.”
In January, the German city of Zittau, just across the border from Turow, also took Poland to the same court on the same grounds. The Czech government filed the claim after talks with Warsaw were inconclusive.
After the ruling was issued, PGE posted on Twitter to criticise the court's decision, saying it was putting Poland on a path toward a "wild" path to energy transformation.