A Polish court on Thursday ordered anti-communist dissident and former Polish president Lech Wałęsa to apologize to opposition party leader Jarosław Kaczyński for comments made on Wałęsa’s Facebook page.

Wałęsa suggested that Kaczyński, leader of the currently ruling Law and Justice Party, was responsible for a 2010 air crash that killed Kaczyński’s twin brother and then-president Lech Kaczyński as well as 95 other people. The plane crashed while trying to land at a dilapidated airfield in Smolensk, Russia, during a heavy fog. Wałęsa accuses Kaczyński, who was in Warsaw, Poland, at the time, of having knowledge of the bad conditions and ordering by phone for the plane to land anyway.

This claim has been made before by critics of Kaczyński, though no evidence has emerged to support it. An investigation of the crash laid the blame on under-trained military pilots, who committed a “cascade of errors while trying to land in terrible conditions.”

Wałęsa and Kaczyński have had an antagonistic public relationship for many years. Kaczyński and his twin brother served as Wałęsa’s advisers while he led the 1989 movement that successfully removed the Communists from power in Poland. Some time after Wałęsa was elected president in 1990, he and the Kaczyńskis had a bitter falling out and became fierce opponents.

The court ordered that Wałęsa must publish his apology on his Facebook page, as well as in a newspaper and a weekly magazine. In making the ruling, the judge stated that “Freedom of speech is not an absolute freedom.” Wałęsa has said that he will appeal the verdict.