Poland, an EU member since 2004, is often seen as a troublemaker in the bloc. The tensions have heightened since the conservative Law and Justice (PiS) party came to power in 2015.
As PiS seeks another mandate in the general election on Sunday, here are the main points of contention between Warsaw and Brussels:
European Council president
In 2017, the government in Warsaw tried to block Poland's Donald Tusk, now the opposition leader in the country, from being re-elected for a second term as president of the European Council.
Tusk, a figure of hate for the Law and Justice party, continued in his post thanks to the support of 27 countries with only a single country voting against, Poland.
Rule of law
The PiS government has in recent years been engaged in a standoff with the EU over its judicial reforms, with Brussels accusing it of undermining the independence of Polish judges.
Poland is subject to the procedure of Article 7 of the EU Treaty, the most powerful European mechanism, which can lead to the suspension of voting rights in the European Council.
The country is still blocked from getting more than 35 billion euros ($37 billion), its share of the European Recovery Plan, and other EU funds, while paying large fines for non-compliance with European court decisions.
National laws supremacy
In July 2021, under the influence of the ruling party, the Polish Constitutional Tribunal declared the decisions of the Court of Justice of the EU (CJEU) regarding Polish judicial reforms to be unconstitutional.
Tensions rose again four months later when the same court challenged the supremacy of European law by judging certain articles of the EU treaties "incompatible" with the Polish constitution.
Following judgments contesting the primacy of European law, the European Commission referred Warsaw to the EU court in 2023.
EU climate policy
In 2022, Poland filed a complaint with the CJEU against climate policies approved by the EU.
According to Warsaw, these policies have not been properly evaluated, have exceeded the competencies of Brussels, and threatened Poland's economy and energy security.
The EU has adopted by majority vote a series of climate acts aimed at reducing the bloc's net greenhouse gas emissions by 2030 to 55% compared to 1990 levels, and helping its members comply with the Paris climate accord.
Turow mine
In 2021, the Czech Republic took legal action at the EU level against neighbouring Poland for the diversion of water caused by the enormous open-air Polish coal mine of Turow and for non-compliance with climate rules.
Poland was ordered to close the site. But arguing its energy security depends on coal, Poland has refused to comply with the decisions of the EU court and maintained the operation of the site.
Warsaw has ultimately come to an agreement with Prague, paying it millions of euros in compensation for the withdrawal of the complaint.
Bialowieza forest
In 2018, Poland was condemned by the CJEU for having violated environmental protection legislation with massive logging of trees.
According to the CJEU, these operations led to the disappearance of part of the large natural forest of Bialowieza (north-east), a protected site, classified by Unesco in the Natura 2000 programs.
Warsaw argued logging was necessary to stop wood-eating beetles from spreading, but eventually stopped felling the Bialowieza trees.
Migrations
Poland, like its EU ally Hungary, has opposed the rules on asylum seekers sharing scheme within the bloc, in particular, the system of refugee quotas introduced during the crisis of 2015.
This year the two countries tried, so far to no avail, to block a compromise on a European migration policy reform.
'LGBT-ideology free' zones
In 2021, the European Commission launched an infringement procedure against Poland for its "LGBT ideology-free zones", established by resolutions adopted in around a hundred regions, municipalities, and other local authorities.
Under pressure from Brussels, which called for respect for dignity and human rights, and the threat of blocking funds for the municipalities concerned, the majority of them have since scrapped the acts.
Brussels has withdrawn its legal complaint.
