To be clear this is an international court and its rulings are unfortunatly ignored in many cases. However it also happens to be the international court, for which it happens the least and it has a good reputation globally. So a strong precedent set by the European Court for Human Rights would set a strong precedent for European courts and work as a strong argument to bring governments into complying with the Paris Accord.

So the big win is that this can create a field day to sue European fossil fuel companies and the like.