As Poland becomes the latest country to erect a stumbling block in the path of the EU's Lisbon Treaty, the BBC's Adam Easton, in Warsaw, examines why.
Poland's president has provided the first challenge for Mr Sarkozy
Polish President Lech Kaczynski's announcement that he will not yet sign the Lisbon Treaty highlights the competing power centres in the EU's largest new member and their different approaches to Europe.
In this particular case, Mr Kaczynski may well end up having the final say because, even though the Polish parliament has already approved it, he must sign it to complete the ratification process.
But Poland's Prime Minister Donald Tusk - who actually shapes much of the country's foreign policy - says EU leaders should search for ways to implement the Lisbon Treaty.
Asked by the newspaper Dziennik whether he would ratify the Lisbon Treaty, Mr Kaczynski replied: "At this moment, it's pointless". He did not rule out ratifying it in the future.
"It's difficult to say how this will end. However, it's not serious to say, 'if there is no treaty, there is no EU'... The EU worked, is working and will work," he told the newspaper.
Mr Kaczynski's comments are not entirely surprising because, like his twin brother Jaroslaw, the country's former prime minister, he is against deeper European integration.
"The president wants to position himself as the defender of the remnants of Polish sovereignty because it appeals to a quarter to a third of the electorate," Pawel Swieboda, director of an EU think-tank, DemosEuropa, told me.
Both brothers would also be happy to see the Nice Treaty - which currently governs the way the EU operates and gives Poland disproportionate strength - remain in force for a while longer.
The Lisbon Treaty would reduce Poland's voting strength.
The president has also played on fears here that the Lisbon Treaty and its Charter of Fundamental Rights would force staunchly Roman Catholic Poland to adopt homosexual marriages and a more liberal abortion law.
In a televised address to the nation, he even suggested that the charter would make it easier for Germans to reclaim property they lost during and after World War II.
But Mr Kaczynski's comments reveal the sharp division between himself and his government.
Prime Minister Tusk, like the majority of the public here, is broadly enthusiastic about the EU.
In a survey conducted earlier this month, 70% of Poles said EU membership was positive, and 69% said it had improved the country's international position.
Shortly after the Irish referendum, Mr Tusk said Europe would find a way to implement the Lisbon Treaty.
It is not exactly clear who has the upper hand in this dispute.
The Polish constitution says that once the parliament has ratified a treaty, the president must sign it. But the constitution does not specify a time limit.
Poland's Prime Minister Tusk (left) is, for the most part, a fan of the EU
In practice, Lech Kaczynski could continue to refuse to sign the ratification.
The government's recourse would be to take the matter to the State Tribunal but, after the Irish referendum, that seems rather unlikely.
"The government is what matters here. Mr Kaczynski will not have much of a bearing on this process. He can be an irritant, but he's just undermining his own influence," Mr Swieboda says.
"After today's interview I think Mr Kaczynski is simply not going to be a player in European politics."
However, on the day France takes over the EU presidency, its leaders might be forgiven for wondering what is the official Polish policy.