Slovakia has changed its constitution, enshrining into law recognition of only two sexes – male and female.
The legal change, which passed in a knife-edge vote in parliament, also restricts adoption to married heterosexual couples and prohibits surrogate pregnancies.
The constitutional amendment was defined as enshrining “sovereignty in cultural and ethical matters”.
Critics including Amnesty International have warned the change would make life more difficult for LGBT people, saying it brings the country’s legal system closer to Hungary’s illiberal government or Putin’s Russia.
Parliament’s backing of the amendment came as a surprise to observers, with even the prime minister conceding as late as Thursday it might not pass.
Fico’s government – a coalition of populist, leftist and nationalist parties – needed at least 90 votes in the 150-seat Slovak National Council to change the constitution, but realistically only control 78 seats.
However, in the end 12 opposition MPs voted with the government. The conservative opposition Christian Democrats had long been expected to lend their support, but several members of former prime minister Igor Matovic’s Slovakia movement added their votes at the last minute, tipping the scales.
Matovic described them as traitors.
The populist-nationalist government argued the amendment was necessary to protect what it described as “traditional values”.
Prime Minister Robert Fico praised the vote and said his party would have a shot of liquor to celebrate their success. “This isn’t a little dam, or just a regular dam – this is a great dam against progressivism,” he declared.
He had previously argued that what he called liberal ideology was “spreading like cancer”.
Slovak legal scholars say a constitutional amendment enshrining the primacy of the Slovak constitution over EU law is a direct challenge to the European Union, and will lead to legal battles and potential sanctions.
Some said the move was merely a ploy by Fico to distract attention from falling poll ratings and unpopular policies.
“The Slovak constitution has fallen victim to Robert Fico’s plan to dismantle the opposition and divert attention from the real problems of society, as well as the austerity measures he had to pass,” Beata Balagova, editor-in-chief of Slovak daily SME, told the BBC.
“Fico does not genuinely care about gender issues, the ban on surrogate motherhood, or even adoptions by LGBTQ people,” she added.
Most opposition MPs stayed away from parliament and Progressive Slovakia, which is leading the polls, said the betrayal marked the end of any potential co-operation with Matovic and his party.
President Peter Pellegrini said he would sign the amendment.
“At a time of enormous division within Slovak society, a constitutional majority is an important signal that there is agreement on a specific issue across the political spectrum, and it must be respected,” he said following the vote.
Robert Fico’s Smer-Social Democracy party has now strayed so far from the progressive values espoused by Europe’s centre-left mainstream that reports say it will be formally expelled from the Party of European Socialists (PES) at a conference next month.
Smer was suspended in 2023 after forming a coalition with the far-right Slovak National Party.
Since then, Fico has angered European allies by meeting Russia’s Vladimir Putin four times in less than 12 months.
Smer has not commented on the reports.