Under the handover deal, Beijing promised Hong Kong could keep key civil liberties, as well as judicial and legislative autonomy, for 50 years.
That landscape is now changing and the effects of the new law are being felt at the grassroots.
On Monday the city’s government ordered books that might breach the bill be taken from the shelves for review and possible removal.
“In accordance with the four types of offences clearly stipulated in the law, the school management and teachers should review teaching and learning materials in a timely manner, including books,” the Education Bureau said.
“If they find outdated content or content that may concern the four aforementioned offences, they should remove them,” the bureau added.
The law names four national security crimes: subversion, secession, terrorism and colluding with foreign forces.
The titles of books to be reviewed have not been made public, but the order comes two days after Hong Kong’s libraries said they were pulling titles by the activist Wong and at least two other pro-democracy figures.