2019 Hong Kong extradition bill
However, organizations like Amnesty International and many Hong Kongers saw that the law could also be used in another way.  The law could allow the government to arrest almost any Hong Konger suspected of a crime and send them to be tried in mainland China instead of in Hong Kong.  Mainland China has a reputation for unfair trials.  They worried that the government would use this to arrest Hong Kongers who spoke against the mainland government and bring them to China as political prisoners and scare the people of Hong Kong.