Jarosław Kaczyński files Supreme Court cassation appeal in defamation case against Radosław Sikorski

Legal challenge reaches Supreme Court

Law and Justice (PiS) leader Jarosław Kaczyński filed a cassation appeal to the Supreme Court challenging a March 2026 appellate ruling that dismissed his civil lawsuit against Foreign Minister Radosław Sikorski. The press office of the Warsaw Court of Appeals confirmed on 7 October 2026 that it received the appeal documents for transmission to the highest judicial instance. The civil dispute centers on the protection of the personal rights and memory of late President Lech Kaczyński, who died alongside First Lady Maria Kaczyńska and 94 other passengers in the 10 April 2010 Smolensk plane crash. Kaczyński initiated legal proceedings in January 2021 after Sikorski, then serving as a Member of the European Parliament for Civic Platform, published social media comments evaluating the late president's responsibility for the crash.

The origins of the dispute and court proceedings

The conflict originated on 14 January 2021 when Sikorski replied on Twitter to journalist Konrad Piasecki, who had expressed support for naming a street in Warsaw after Lech Kaczyński. Sikorski wrote that Lech Kaczyński was a mediocre president who substantially contributed to the Smolensk disaster, referencing existing memorials at Wawel Castle and Piłsudski Square while calling for an end to unjustified memorialization. On 17 March 2023, the Warsaw District Court ruled in favor of Kaczyński and ordered Sikorski to publish a dedicated apology on his social media account and pay legal costs. Sikorski appealed the first-instance verdict, leading to the March 2026 appellate judgment that reversed the ruling and dismissed the claim entirely. Sikorski's attorney, Elżbieta Kosińska-Kozak, noted that the appellate court recognized Sikorski's right to express factual criticism based on objective records and personal observations, including a shared flight to Georgia in 2008.

Political clash over crash findings

Following the notification of the cassation appeal on 7 October 2026, Sikorski criticized the legal maneuver in a public statement on the platform X, arguing that the court filings contradicted the political rhetoric of the Law and Justice party.

I remind that this is a case where Kaczyński submitted the Miller Commission report in court as evidence, which confirmed the occurrence of an accident and excluded an assassination. For the needs of politics, there are delusions about an assassination, and for the needs of compensation and the lawsuit, there is an accident.

Kaczyński addressed the cassation appeal during a press conference at PiS party headquarters later that day, maintaining that his legal claims remained justified across every court proceeding.

In cases where my late brother was accused of being somehow complicit in the disaster, we initiated trials and each time we won them in the first instance, because our evidence was very solid.

Kaczyński noted that while he considered the Miller report scandalous, the document itself concluded that the late president played no direct role in the catastrophe. The Polish government under the Ministry of National Defence had previously dissolved the Antoni Macierewicz investigative subcommittee in December 2023, restoring the Miller Commission report as the state's sole binding document on the disaster. The Supreme Court will now determine whether the appellate court committed procedural or legal errors when it dismissed Kaczyński's claim.