The ruling by the court in Strasbourg, France, is a response to a 2007 case in Lausanne, Switzerland, in which Dogu Pernicek, leader of the leftist Turkish Workers Party, was found guilty of "denying the Armenian genocide for racist motives."
Denial of genocide is a violation of Switzerland's anti-racism law.
Pernicek's testimony did not deny the massacres of Armenians by the Ottoman Empire, which ruled Turkey during World War I, the human rights court said, but noted he was active at conferences in which he described the Ottoman Empire's alleged genocidal motives as an "international lie."
The judgment came as the French newspaper Le Monde reported a law banning denial of the Armenian genocide, an election promise of President Francois Hollande, will be sent to the French Parliament within months.
A similar French law, passed in 2011 to the anger of Turkey, was declared unconstitutional, Radio France Internationale reported.
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