(CNN) The head of Poland's Supreme Court, Małgorzata Gersdorf, entered the court building Wednesday in defiance of a controversial new law that has escalated tensions between the European Union and Poland's government.
The law, which came into force at midnight, mandates that all Supreme Court judges over the age of 65 must retire and will force 27 of the 72 judges off the bench, according to the European Union.
"My presence here is not about politics, I am here to protect the rule of law," Gersdorf, who is 65, said at the court's entrance, surrounded by supporters and opposition politicians.
Video footage tweeted by local radio journalist Mariusz Piekarski showed her making her way through chanting crowds on Wednesday, holding white roses in her hand.
Critics say that the Polish government is eroding the rule of law and that its so-called reforms are intended to give it control of the judiciary. But the government, led by Prime Minister Mateusz Morawiecki, insists that the measures are needed and will strengthen democracy.
"Each EU state has the right to shape their legal system according to their own traditions," Morawiecki told the European Parliament in Strasbourg, France, on Wednesday.
Presidential aide Paweł Mucha told state media Tuesday that Gersdorf's forced retirement would be "in line with binding laws" and that current judge Józef Iwulski would fill her position.
But Gersdorf argues that the new rules contravene the constitution -- under which she should serve a six-year term, ending in 2020 -- and cannot be implemented, Reuters reported.
"The constitution obliges me to a six-year term and I must proceed according to the constitution," she was quoted as saying by the Polish Press Agency (PAP) on Tuesday.
The 27 judges affected by the new law could submit an application to Poland's President -- an ally of the governing Law and Justice (PiS) party -- to extend their mandate. According to the Supreme Court, 16 of them did so. However, Gersdorf said she "did not submit and will not submit" such an application.
The other 26 judges forced off the bench by the new law also showed up for work Wednesday, according to PAP.
"This is a watershed moment for the Polish judiciary and indeed for the whole political system," said Piotr Buras, head of the Warsaw office of the European Council on Foreign Relations (ECFR), an independent think tank. "It may have some very far-reaching consequences and implications for further political development in Poland."
Besides the dismissal of the 27 judges, the National Judiciary Council -- which following reforms last year is controlled by the ruling party -- can also now nominate more than 50 new judges, Buras said.
If that goes ahead, the ruling party will effectively control the Supreme Court, he said, which as well as being the country's highest court of appeal has responsibility for ensuring the validity of elections.
On Tuesday, the dispute triggered protests in front of the court in the capital, Warsaw, which Gersdorf also attended. Hundreds gathered to wave EU flags and placards reading "constitution" to show their support for the supreme court judge.
Further demonstrations are planned outside the court on Wednesday evening.
The European Commission, the EU's principal administrative body, has contested the law and on Monday announced it had launched an infringement procedure against it.
The legislation would "undermine the principle of judicial independence, including the irremovability of judges," it said in a statement. The Polish government has one month to respond to the commission's Letter of Formal Notice, it said.
Nonetheless, the dispute has highlighted the limitations on what the EU can do to deal with member states that act contrary to the bloc's fundamental principles.
Since the conservative PiS came to power in 2015, the EU has clashed repeatedly with Morawiecki's government over judicial reforms that have broadened the government's power over the Supreme Court and national council of the judiciary, which appoints judges.
In December, the European Union triggered an unprecedented disciplinary process against Poland for a "serious breach" of its values.
The European Commission warned of a "clear risk of a serious breach in the rule of law" posed by the legal reforms and recommended that the bloc's leaders invoke Article 7 of the Lisbon Treaty.
Under Article 7, the most serious punishment that could be inflicted would be the removal of Poland's voting rights in EU institutions. However, that would require a unanimous vote to be passed and Hungary's right-wing government has already said it would reject the proposal.
The ECFR's Buras said the decision to launch the infringement procedure against the Supreme Court law had come "very late" -- and too late to prevent the dismissal of the 27 judges -- but was still a significant step.
It opens the door for the European Court of Justice to prevent the nomination of new judges to the Supreme Court, he said, and in combination with the threat of Article 7 proceedings will significantly increase the pressure on Poland's government.
The move also signals to other countries such as Hungary that the EU is ready to act in defense of its principles, he said.
Within Poland, protests against the ruling party's latest actions are likely to be smaller than other recent demonstrations because many people want to see reform of the judiciary, Buras said -- and don't realize that what the ruling party is doing is "outrageous."
Amnesty International last month warned that Polish citizens' human rights were at risk from "systematic erosion of guarantees for an independent judiciary" and urged the Polish government and parliament to amend the laws in question.
It also called for the government to "ensure that judges can exercise their judicial functions free from retaliatory action or other forms of pressure, including politically motivated disciplinary proceedings, harassment and intimidation."