The European Commission has asked the EU's top court to rule on whether Poland has violated “the principle of judicial independence” in response to a crackdown on the Polish Supreme Court that critics say undermines the country's checks and balances.

The big picture: Poland's government, controlled by the right-wing populist Law and Justice party, implemented a law in April that cut the retirement age for Supreme Court judges from 70 to 65, forcing 27 out of 72 sitting judges to step down. The EU passed a motion last year censuring Poland for undermining Europe's democratic values, though repercussions are unlikely due to Poland's alliance with Hungary and its illiberal government.