Hong Kong's ability to remain a leading international financial hub since China resumed control over the city in 1997 has rested in good part on the robust independence and neutrality of its courts.

Yet there are signs the national government may no longer accept the full authority of Hong Kong's judiciary to review actions by the local administration. Its impatience has its origins in the city's move in October to adopt a ban on the wearing of face coverings at a wide range of public gatherings by invoking a colonial-era law called the Emergency Regulations Ordinance in response to violent confrontations between protesters and police.

Last week, the city's High Court found the restriction on the constitutional rights of Hong Kongers occasioned by the anti-mask law unjustified. The judges concluded that while a prohibition on face coverings at unlawful assemblies was reasonable, extending the ban to a wide range of lawful and peaceful gatherings was a disproportionate infringement on guarantees of free expression and assembly found in the Basic Law, the city's mini-constitution.

The court also questioned the use of the Emergency Regulations Ordinance as the move shifted lawmaking authority from the legislature into the hands of the chief executive on uncertain and subjective grounds.

The rejection of the mask ban by the court was interpreted very differently across the political spectrum. For protest supporters, it was a welcome respite and victory, even if small. It was a reminder that Hong Kong's judiciary remains robustly independent even as other institutions of governance appear to be on shaky foundations.

For opponents, the ruling was seen as improper judicial interference in a political matter. Strikingly, a spokesperson for the National People's Congress Standing Committee on the mainland said that only his body had the right to judge whether or not Hong Kong's laws were constitutionally valid.

Depending on how his comment is read, the implications for Hong Kong's judicial autonomy -- as promised under the "one country, two systems" governance model laid out in the 1984 Sino-British Joint Declaration -- are stark.

As guardians of the rights guaranteed under the Basic Law, Hong Kong courts have declared a number of laws unconstitutional since 1997. If the NPC statement is to be read as a plan to entirely deny local courts the power to review actions of the government for consistency with the Basic Law, that would be a radical restriction on their role.

If, however, the statement is understood only as an angry reminder that the Standing Committee has the ultimate word on interpretation of the Basic Law, that would be largely uncontroversial. The "one country" element of "one country, two systems" necessitates that the final say on the meaning of the city's constitution exists at that level.

But how that power is used matters. In the past, this was understood by the central authorities. The Standing Committee has issued formal interpretations of the Basic Law only five times since 1997. If it plans to start doing so more frequently, that too will bring a consequent reduction in Hong Kong's judicial autonomy.

It remains to be seen which path Beijing will choose. Since the outcry in Hong Kong over its initial statement, the NPC has not repeated its stance that local courts have no ability to review government actions and laws. But with the government appealing the High Court's ruling, this could create an opportunity for the Standing Committee to issue an interpretation that would be binding on all Hong Kong courts.

Whatever the outcome, this episode has thrown into stark relief fundamental challenges that underpin the "one country, two systems" model.

The "two systems" reflect a fundamental difference between this quasi-democratic capitalist city and the authoritarian quasi-socialist state it sits within about the role of the judicial branch: should judges be neutral arbiters, to the greatest extent possible, regardless of the political consequences of their decisions, or should they be enlisted as part of the machinery of the state in the service of its policy goals?

Whether Beijing can continue to tolerate a part of China that has such a radically different perspective on judges' proper role will have enormous consequences. Hong Kong's success has been built in no small part on the confidence of the international community in the neutrality and reliability of its judiciary.

If in the coming years the central authorities force the local courts to ultimately bend to their wishes or those of the local government, then Hong Kong will gradually lose its status as one of the preeminent financial centers of the world.

Stuart Hargreaves is an associate professor of law at the Chinese University of Hong Kong.