Editor's note: This is the fifth in a series of articles exploring the various aspects of the "One Country, Two Systems" concept governing Hong Kong since the return of its sovereignty to China.

If one person had the biggest impact on the news this year, it was Edward Snowden, former Central Intelligence Agency employee and former National Security Agency contractor. With Snowden again making the headlines in the past few weeks, perhaps it is time to use his escape to Hong Kong to examine another element of the "One Country, Two Systems" principle and the city's independent judicial system.

When Snowden first escaped from the US, Washington began pressuring the Hong Kong government to extradite him under agreements the city had signed. The local government was, in turn, pressured not to hand Snowden back by both public opinion and a desire to know more about the NSA's spying on Hong Kong organizations such as Chinese University of Hong Kong. In the end, the government let Snowden leave rather than going through all the trouble of detaining him.

However, what if the government had decided to pursue extradition? What would have happened then?

Snowden would not have been returned right away; instead, his case would have gone to court, where a judge would then decide whether Snowden would be returned to American hands. If the local legal system decided that Washington's request was politically motivated, it could reject the extradition request. Thus, Snowden's extradition request had to go through two institutions: The Hong Kong government, who would first decide whether to meet Washington's request, and the local courts, who would then decide whether the request was made for political reasons.

The mainland is not entirely absent from the discussion of extradition: The Hong Kong government does not have the jurisdiction to extradite mainlanders, and Beijing can advise the Hong Kong government when not to extradite someone, for reasons of national security. The government undoubtedly pays very close attention to what Beijing believes it should do.

Whatever degree of control Beijing may have over Hong Kong's government, this control does not extend to the courts. If Snowden had ever gone before a Hong Kong judge, then his fate would have been entirely out of the Hong Kong government's, and out of Beijing's, hands. In fact, this may have been the reason why Snowden was persuaded to leave: The Hong Kong government could not give him a guarantee that the courts would reject Washington's extradition request.

Such a complex story rarely appeared in the foreign media. Very few American observers thought that Hong Kong had any independent say in the matter, arguing that both the Hong Kong government and the courts would merely rubber-stamp whatever Beijing told them to do.

Many foreign countries (including the US) have praised the strength of Hong Kong's rule of law. Hong Kong judges have defied the Hong Kong government on several occasions, such as the Court of Final Appeal's judgment that any Chinese child born in Hong Kong was entitled to permanent residency.

Admittedly, Hong Kong's courts do not have the power to interpret the Basic Law, which lies with the Standing Committee of the National People's Congress, instead of the Court of Final Appeal. However, this only concerns constitutional matters and has been rarely invoked since the handover.

The fact remains that the Hong Kong legal system is based on very different principles than its mainland counterpart. Hong Kong uses the old British system of common law, which ties the city to an international legal tradition. Hong Kong courts are even allowed to invite judges from other common law jurisdictions to sit on its cases. Combine these different legal principles with the city's exclusion from the mainland's legislation, and we have a uniquely independent judiciary.

It is difficult to imagine any other country's courts behaving so independently. Would a local court in, say, California invite a judge from another country to sit on a case? The US Supreme Court gets into enough trouble when it cites foreign cases in its legal opinions. Or, on an even more fundamental level, could we imagine a British county with its own legal tradition and its own judges?

Many people argue that Hong Kong's strong rule of law is an advantage the city has compared with the mainland. This is clearly true, and it is a strength that needs to be preserved. However, when we praise the city's rule of law, we are actually revealing another important part of Hong Kong's autonomy, and another reason why this city is unique in today's world.

The author recently graduated with high honors from Harvard University and is doing an MPhil in International Relations as a Clarendon Scholar. His writings have appeared in some leading regional and local publications.

(HK Edition 12/23/2013 page1)