The national security law for the Hong Kong Special Administrative Region (HKSAR) is "consistent with China's constitutional scheme which places supreme power in the central government, as befitting a unitary system," a renowned scholar has said recently.

"The best way to comprehend the constitutional-legal angle of the entire issue is to recognize that unlike the United States federation, China has a unitary system," James C. Hsiung, a professor of politics and international law at New York University, said in an interview with Xinhua via email.

"The concept may sound quaint to the American ear, but the fact is that out of the United Nations' 193 member states, 166 have a unitary system of government," he added.

In China with a unitary political system, supreme power is held by the central government, which duly devolves power upon lower-level governments, including special administrative regions, the expert said.

"The important thing in a unitary system, as different from a federal system, is that the central government, following the devolution procedures, may initiate laws, not just policies, for a lower-level government," he said.

Hence, the national security law for the HKSAR enacted by the National People's Congress (NPC) is "constitutional and consistent with well-established tradition," Hsiung said.

"And between the central and lower-level governments, there exists a relationship of superordination and subordination, not found in a federal system," he said.

According to the 1984 Sino-British Joint Declaration on the Question of Hong Kong, Hong Kong will be "directly under the authority" of the Chinese central government after its return to China, the expert said.

Besides, the HKSAR will "enjoy a high degree of autonomy, except in foreign and defense affairs, which are the responsibilities of the central government," he added.

Stressing "the exception, from HKSAR's autonomy, of both foreign and defense affairs, under which security matters would naturally fall," Hsiung said "a later clause explicitly declares it is the central government's responsibility to protect Hong Kong's 'public order,' which is synonymous with public security."

Based on the HKSAR Basic Law, the NPC "authorizes the HKSAR to exercise a high degree of autonomy," and the NPC Standing Committee "may add to ... the list of the (national) laws" that are applicable to Hong Kong, the expert said.

"Should anyone challenge the NPC on its authority to enact a national law (security law included) for the HKSAR," he said, the Basic Law "is a direct, unequivocal answer."