The European Union's top court ruled Monday that a Polish law that pushed Supreme Court judges into early retirement violates EU law, a setback for Poland's right-wing government but a move welcomed by critics who worried the measure would cause a serious erosion of democratic standards.

In its ruling, the European Court of Justice said the measures breach judicial independence. An interim decision from the Luxembourg-based court in November ordered the Polish government to reinstate judges who were forced to retire early and to amend the law to remove the provisions that took about one-third of the court off the bench.

The court said the law "undermines the principle of the irremovability of judges, that principle being essential to their independence."

There was no immediate reaction from Poland's government, but the decision is a blow to the ruling authorities, who since winning power in 2015 have increasingly taken control of the judicial system.

The government and president have said they wanted to force the early retirement of the Supreme Court judges as part of a larger effort to purge communist-era judges.

But legal experts say that argument holds no water because most communist-era judges are long gone from the judicial system 30 years after the fall of communism. Many critics believe the true aim is to destroy the independence of the Polish judiciary.

The biggest fear is that the judiciary could become so politicized that those not favored by the ruling authorities could be unfairly charged with crimes and sentenced, essentially deprived of fair hearings. Though a separate court, the Constitutional Tribunal, and other bodies are already under the ruling party's control, many judges have continued to show independence, ruling against the authorities, even the justice minister, in recent cases.