The new law expands on previous laws governing national secrets, and comes as relations between Beijing and Washington are deeply strained over military tensions and deep economic competition.
NCSC said the law expands China’s definition of espionage from covering state secrets to any documents or data that the government says could be labelled national security-related “due to ambiguities in the law”.
The law could “create legal risks or uncertainty for foreign companies, journalists, academics and researchers”, it said.
The law comes amid more pressure from Beijing on foreign advisory firms operating in the country.
In March police closed the Beijing office of US due-diligence firm Mintz Group and arrested five local staff members.
The following month, US consulting giant Bain & Company said employees at its Shanghai office had been questioned.
The new law has spooked foreign and domestic firms as they try to decipher authorities’ intentions – and crucially, pinpoint what is off-limits.
“Companies are scrambling to figure out protocols to protect their staff. But the definitions are so vague,” an employee of a major international auditing firm told AFP in May.
“No one knows whether they have crossed a line or not, or where the red line is.”