The legal warfare between the European Commission and Poland and Hungary over LGBTQ rights, asylum rights and judicial reform raised concerns Thursday that the EU legal order is under threat.
Brussels has launched a series of challenges to its prickly eastern members over what EU officials see as their challenge to European values and the rule of law -- and won some early victories.
But Warsaw and Budapest have fought back just as hard, leaving some to wonder whether a battle is building over the very principle that EU law holds sway over the member states.
"There could be a spillover effect, where we could see a whole series of EU countries questioning these principles in a more or less aggressive way," EU Justice Commissioner Didier Reynders said.
"If we allow this to develop, it is obviously a challenge to the union itself."
Reynders' warning came as Hungary's Prime Minister Viktor Orban reacted with fury to the announcement that Brussels had launched a legal challenge to his so-called "anti-paedophilia" law.
"If the European Union wants to interfere in matters and laws covered by the constitutions of other countries, that could shatter the entire EU," Orban's cabinet chief Gergely Gulyas said.
Separately, Poland's prime Minister Mateusz Morawiecki rejected a ruling by the European court of Justice that found that a central part of Poland's judicial reforms was a breach of EU law.
- Illegal breach -
"I cannot allow Poland to be treated in a separate, less favourable way, to be discriminated against," he declared, alleging that the European Commission had exceeded its authority.
"Nowhere in the treaties have the powers to reform a legal system been transferred ... to the level of the European Union," he argued.
A "deeply concerned" European Commission, the Brussels-based guardian of the treaties, vowed to "make use of its powers" and ensure that Poland accept the primacy of European law.
Poland has also been targeted over LGBTQ rights, with Brussels opening a case on Thursday over its so-called "LGBTI ideology free zones" that could also end up in court.
And yet another front in the conflict was opened on Thursday when the commission announced it was taking Hungary to court over its decision to tighten rules for refugees and migrants seeking asylum.
Citing the threat of the Covid-19 pandemic, Hungary has said asylum-seekers must register with an embassy outside the country before arriving, a move Brussels' says is an illegal breach of refugees' rights.
Orban's international spokesman Zoltan Kovacs dismissed the argument.
"The European Commission made it clear that it wants Hungary to allow migrants in, so that they can submit their asylum claims here," he tweeted.
"If we comply with the EC's decision, instead of leaving, these migrants will want to stay in Hungary.... We won't let Hungary become a country of immigrants."
Both Hungary and Poland are ruled by right-wing, socially conservative governments whose policies have raised rule-of-law questions.
- Religious beliefs -
Hungary's "anti-paedophilia" law, which among other things bans the "promotion" of homosexuality and gender reassignment to under-18s, came into force last week despite many warnings from Brussels.
EU commission chief Ursula von der Leyen said last week that the EU executive would force Hungary to repeal or modify the law.
"Europe will never allow parts of our society to be stigmatised: be it because of whom they love, because of their age, their ethnicity, their political opinions, or their religious beliefs," she told MEPs.
Hungary's legislation was billed as a way to protect children, but opponents argue that it conflates paedophilia with homosexuality and stigmatises the LGBTQ community.
In Poland, around 100 towns and villages have adopted the "anti-LGBT" resolution, which some describe as a "charter for family rights".
They cover about a third of Polish territory and are mainly located in the country's east and southeast, traditionally very Catholic.
"The commission considers that Polish authorities failed to fully and appropriately respond to its inquiry regarding the nature and impact of the so-called 'LGBT-ideology free zones'," a statement said.
The Polish law on reforming the judiciary, which came into force in February last year, prevents judges from referring questions of law to the European Court of Justice.
It set up a "disciplinary chamber" to oversee Polish judges, with the power to lift their immunity.
The government argues the reforms tackle corruption and end Communist-era legacies in the judiciary.
But the European Commission says they undermine judicial independence, and Poland could now face financial penalties after the Court of Justice ruled Thursday it had "failed to fulfil its obligations under EU law".