Among the global commons, the High Seas, the atmosphere, Antarctica, outer space and cyberspace, only cyberspace, is an artificial "space".

Although this virtual space is dependent upon real space, it is not bound by real space in terms of territorial boundary. Consequently, although cyberspace has similarities with the other global spaces, it also has differences.

In terms of similarities, both cyberspace and real space store and transport goods. In terms of differences, in real space, the goods stored and transported are tangible items, but in cyberspace, the goods stored and transported are intangible, as they are information and ideas.

A critical question then arises, does sovereignty, which is applicable to real space, similarly apply to cyberspace?

The answer is, largely, in the affirmative, at least for national security purposes.

For at least three national security reasons, sovereignty should apply to cyberspace.

First, for political, diplomatic, security, defense and strategic purposes, which are the traditional national security interests of a state, the state authority has legitimate reasons to keep cyberspace within its traditional sovereign control.

Second, to protect its intellectual properties, a state authority also needs to enforce sovereignty, so as to retain national competitiveness. This is the same no matter in real space or virtual space. Such interests are now increasingly viewed as an extended part of national security.

Third, a state's authorities have the sovereign right to keep prohibited "goods" whether real or virtual from the public.

Generally speaking, there is not much dispute over the first two. Keeping national secrets confidential and safeguarding intellectual property rights, no matter in technical innovations or cultural creation, are a global norm and practiced in both the physical and cyber realms.

On the third, there is no controversy over restricting the spread of pornography, racialism and terrorism, as a state government has perfect reason to justify its move to outlaw them for the sake of national security. However, there are different views when it comes to political ideas and values.

In terms of separatism, there certainly exist some differences among nations. For instance, China is opposed to voices promoting Taiwan and Tibet "independence". Other countries may be less sensitive about such separatist views as they do not face such secessionist sentiment.

The best approach is to respect the sovereign decision of each country depending upon its own justification of national security.

Then, there is a sharp division over the value of the free flow of information. On the one side are those upset by the exercise of sovereignty over cyberspace because it obstructs the freedom of information, while on the other there are those who are worried about the challenge to national security due to the flow of information on the internet.

Generally speaking, it is in this area that disputes arise in regard to the appropriateness of applying sovereignty to cyberspace. A state government that is disinclined to soften its sovereignty over its real territory, is unlikely to do so over its virtual "territory". While most agree there should be a balance between the free flow of information and prohibiting the flow of dangerous information; where that balance lies varies.

Sovereignty is as relevant in cyberspace as real space. In order to maintain national security and social order, sovereignty has to be exercised in cyberspace.

（The author is a professor and associate dean at the Institute of International Studies, Fudan University.）

Editror: Ellen Liu