BEIJING—China adopted a sweeping national-security law that the government says is needed to counter emerging threats but that critics say may be used to quash dissent and exclude foreign investment.

Approved by the legislature’s standing committee Wednesday, the law sets an expansive definition of national security that outlaws threats to China’s government, sovereignty and national unity as well as its economy, society, and cyber and space interests.

Its passage marked the latest signpost in Beijing’s intensifying crackdown on activism and dissent during the past two years, featuring repression of civil-society groups, heightened monitoring of social media, and sharpened warnings against the spread of Western ideas and influences.

The new legislation forms the centerpiece of a series of proposed security laws, including draft laws on counterterrorism and the management of foreign nonprofit groups. Together, experts said, the laws underpin a push by President Xi Jinping to consolidate his and Beijing’s power and promote a notion of rule of law that doesn’t undermine the Communist Party’s authority.

These laws “reflect the party’s determination to create a garrison state,” said Jerome Cohen, a veteran China legal scholar at New York University. The national security law, he said, is “an ideological platform that guides domestic and foreign policies.

Chinese officials and lawmakers have defended the new law, first proposed last August, as necessary to deal with unprecedented and increasingly complex threats to national interests, ranging from cybercrime to terrorism. “China’s national security situation has become increasingly severe,” Zheng Shuna, vice chairwoman of the National People’s Congress’s legislative affairs committee, told reporters after the law’s passage.

While current laws already give the government wide power and do little restrain abuses by police, experts said the new law will give security agencies stronger legal footing in curbing perceived threats from social activists and government critics.

“This law will legitimize the abuse of power by state and public security bureaus,” saidTeng Biao, a prominent Chinese lawyer who was detained in the past over his rights activism, and is now a fellow at Harvard Law School. “For the Communist Party, the rule of law means using legislation as a tool of control.”

In recent months, the legislation has drawn an unusually broad range of critics. Along with the concerns of human rights groups and Western governments, foreign business groups have also expressed misgivings that the law along with the other proposed measures may be used to restrict foreign investment from telecommunications, banking and any other sector Beijing deems sensitive.

While the final text of the law wasn’t published immediately after the vote, a draft circulated just before contained the same broad definitions of national security that these groups had criticized in earlier versions. At issue for many business groups is the law’s provisions that link economic development with the preservation of national security—a provision that business groups have said could be used to justify protectionist policies.

Rights advocates, meanwhile, have criticized the law for its vague provisions, as well as the lack of detail on what Beijing deems as offenses and what penalties would apply.

Such ambiguities that would “make it impossible for people to know what behavior is actually prohibited,” and allow authorities to prosecute anyone they deem to be a threat, said William Nee, a Hong Kong-based researcher at Amnesty International. “This time the devil is in the lack of detail.”

Ms. Zheng, the legislator, rebuffed criticisms that the law is vague. China’s definition of national interests “is very clear-cut, and isn’t any broader than those set by other countries,” she said. “We welcome all enterprises to operate lawfully and provide lawful services in China.”

Legal experts said the law would likely translate into greater political clout for President Xi. While the law is silent on which state agencies would have oversight on China’s national security apparatus, analysts expect that role to be fulfilled by the National Security Commission that Mr. Xi created and heads, which sets policy on domestic and international security.

The new law also appears to give backing to Mr. Xi’s mounting ideological campaign, which has often invoked patriotism as well as concerns about subversive foreign influences. Among the law’s ideologically tinged clauses, it calls on officials to “strengthen guidance on news, propaganda and public opinion about national security,” and include “national security education” in school curricula.

By Chun Han Wong July 1 2015 in The Wall Street Journal