Jaroslaw Kaczynski, the head of the ruling Law and Justice party, sued Walesa for blaming him in social media posts for the 2010 plane crash in Smolensk, Russia, that killed Kaczynski's twin brother, President Lech Kaczynski, and 95 others, including top Polish political and military leaders.
In one of the posts, Walesa alleged that Kaczynski, "guided by bravado," was on the phone pushing for the plane to land in Russia despite the heavy fog. The allegation has sometimes been made by Kaczynski's critics, but no evidence has ever emerged to prove it.
Judge Weronika Klawonn ruled that these were "heavy accusations" to make without evidence to back them up and argued that there are limits to free speech.
She ruled that Walesa must apologize to Kaczynski in various platforms, including on the radio, on social media and in a personal letter, and must pay court costs.
She said the ruling came amid awareness of the broader political struggle, including Kaczynski's own accusations that his centrist political opponents bore some guilt for the disaster. He has alleged that then-Prime Minister Donald Tusk did not do enough to ensure security for the flight of Lech Kaczynski, a political opponent, and also suggested Russian involvement in the crash, something that was never proven.
Kaczynski had also demanded that Walesa pay 30,000 zlotys ($8,000) to charity but the court did not agree to that.
Neither man was in court for the verdict.
This is the latest in the long history of feuding between Walesa, the 75-year-old founder of the 1980s Solidarity pro-democracy movement that peacefully ended communism in Poland, and Kaczynski, his former ally and aide.
Kaczynski, 69, and his twin, who was a top Solidarity activist, promoted Walesa to be democratic Poland's first popularly chosen president in 1990. They became his closest aides, but soon bitterly fell out with him in still-unclear circumstances. Walesa has claimed that the brothers wanted control over him.
The Kaczynskis alleged that Walesa had been a communist collaborator codenamed "Bolek," which Walesa denies and says documents suggesting that had been forged.
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