This is the gist of the Liu Xiaobo case:

"In 2008, Mr. Liu founded the Charter 08 movement, which sought to elevate the rule of law and bring China into constitutional government: “China has many laws but no rule of law; it has a constitution but no constitutional government.” On December 10, 2008, the 60th anniversary of the UN’s Universal Declaration of Human Rights and 100 years after China’s first constitution was written, Liu released a petition signed by 303 incredibly brave Chinese people in support of the Charter. This was the final straw for the government, which arrested him immediately, and he has been imprisoned since."

Liu Xiaobo's Two Prisons

It is shameful that unlawful imprisonment happens not just in China but in countries all over the world.