The Polish Constitutional Court is due to rule on whether the country”s national law can take precedence over EU law.
Poland has been locked in a dispute with the bloc’s other members over the controversial judicial reforms.
In February 2020, Poland passed new measures which prevented judges from referring certain legal issues to the European Court of Justice.
The country also created a “disciplinary chamber” that would rule on the independence of Polish judges and could lift their immunity to face criminal prosecutions.
The ruling conservative Law and Justice party (PiS) say the reforms are necessary to fight corruption, but EU critics see them as a threat to the rule of law.
Prime Minister Mateusz Morawiecki has referred the case to Poland’s Constitutional Court and says reforms in Poland are an internal matter.
A five-judge panel will give their decision on Tuesday.
If the court rules against the Polish government, the EU Court of Justice can force the country to suspend part of its judicial reforms.
But if the verdict finds that certain EU provisions are unconstitutional, Poland can either amend its Constitution, seek to amend EU law or even withdraw from the bloc.
The Constitutional court’s former judges have recently warned that contradicting the EU judiciary would be “a drastic violation of a member state’s obligations” and would represent “another step towards the country’s exit from the European Union”.
EU Justice Commissioner Didier Reynders had called on Warsaw to withdraw the initiative and said the Polish government’s request challenges the “primacy of European law over national law”.
But Poland’s Justice Minister, Zbigniew Ziobro has dismissed the complaint and says the comments were “evidence of insolence, aggression and a colonial view of Poland”.