After months of delay, Poland’s constitutional court has ruled that some European laws conflict with the country’s constitution, escalating a longstanding dispute with the European Union (EU). The court, which has close ties to the ruling Law and Justice (PiS) party, has effectively placed Poland outside of the bloc’s legal system.

The decision marked a serious turning point for the bloc’s sometimes testy relations with the so-called illiberal democracies of Central Europe. Tens of thousands of Poles protested against the decision yesterday, with at least 100,000 gathering in Warsaw to chant pro-EU slogans. Opposition leader Donald Tusk, a former EU official, denounced Poland’s Supreme Court, which critics say has been packed with pro-government lawyers

He argued the ruling was made by a “pseudo-court . . . by order of the party’s leader, in violation of the constitution, [who has] decided to take Poland out of the EU.” Lech Wałęsa, Poland’s former anti-communist leader, joined the protests in Gdańsk.

The EU’s executive, the Commission responded angrily, with the justice commissioner raising that prospect that the European Court may impose a fine for every day that Poland remains in breach. The Commission reaffirmed the primacy of EU law over national constitutions, adding that it would not “hesitate to make use of its powers under the Treaties to safeguard the uniform application and integrity of Union laws.”

In support of its argument, the Polish court cited a 2020 German Constitutional Court ruling that the European Court of Justice (ECJ) exceeded its authority in a case related to the European Central Bank’s bond-buying program. However, the German Court opposed the manner in which the ECJ had applied European law. It did not challenge its supremacy.

Despite the ruling, the country’s Prime Minister Mateusz Morawiecki announced Friday that “Poland’s place is and will be in the European family of nations.” Support for EU membership is high among Poles, with more than 80% in favor of remaining in the bloc. The “return to Europe” is a slogan, which retains an emotional hold for many Central Europeans, who endured decades of Russian-backed misrule, while talk of a possible Polish departure from the bloc is widely regarded as fanciful.

Certainly, the European Commission and the Polish government have clashed for years, beginning with PiS’s overhaul of the judiciary and coordinated takeover of public media. This summer the government refused to comply with the EU’s request that it dismantle a controversial disciplinary chamber for judges, which the EU says undermines judicial independence.

The EU is in a difficult spot. The primacy of EU treaties over national laws is a core tenet of European integration, but swift and harsh action have not been hallmarks of the bloc’s approach to internal disputes. The EU can, however, apply serious financial pressure, in several ways. It could, for example, withhold covid-19 recovery funds worth up to $58.1bn over the next four years. In addition, the ECJ could fine Poland up to $1.2 million a day for its failure to dissolve the disciplinary chamber. These are powerful sticks for a country that remains deeply dependent on EU funding.

So has PiS painted itself into a corner? Tough EU action could galvanize domestic support for the party, which has framed the bloc’s actions as attacks on Polish sovereignty. But it could also damage it, as voters see vital funds threatened by politicized reforms. The public may sour on a government whose actions are perceived to jeopardize Poland’s membership in the EU for the sake of policies few Poles believe are working.