Amal Clooney laid her case before the European Court of Human Rights on Wednesday against a Turkish politician who denied the 1915 Armenian genocide.

The international human rights lawyer is representing Armenia in a case against Dogu Perincek, the chairman of the Turkish Workers’ Party, who was convicted in Switzerland in 2005 for calling the Armenian genocide an “international lie.”

The Strasbourg-based ECHR later agreed with Perincek that the conviction violated his freedom of expression, and now Switzerland is appealing, with Armenia’s backing as a third party.

“The most important error” made in the earlier ECHR ruling, Clooney said, “is that it cast doubt on the reality of the Armenian genocide that the people suffered 100 years ago.” In her remarks, Clooney noted Turkey’s “disgraceful” record on freedom of expression.

An estimated 1.5 million Armenians were killed by Ottoman Turks in what historians widely consider to be the first genocide of the 20th century, but Turkey has contested the numbers and refused to call it a genocide.

The case could also have wider implications for Europe, where several countries have laws prohibiting public denial of past genocides such as the Holocaust.

Clooney, now arguably the most famous human rights lawyer in the world after marrying actor George Clooney in September, previously represented Greece in its long-running bid to have a collection of classical Greek sculptures returned from the British Museum. She also defended one of three al-Jazeera journalists detained in Egypt.

Read next: Amal Clooney Begins Next Big Human Rights Case

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Write to Noah Rayman at noah.rayman@time.com.