From time immemorial, traditional Chinese fishermen have continuously, reasonably and with certainty plied their trade in the semi-enclosed waters of the South China Sea. These traditional fishing practices date back a long time, have been invariable and unbroken, and conform to basic principles of justice and utility. In effect, these practices have acquired the force of law, crystallized into a privately-held "historic right" and constitute a local custom.

 By way of the crystallization of this right in the possession of its nationals, the Chinese state too has acquired a vested interest in the perpetuation of this "historic right" in the South China Sea. And to the extent that the Nine Dash Line serves as the perimeter of this historically-consolidated right of traditional Chinese fishermen in the South China Sea, the line has a durable basis in international law and is fully deserving of its protections.

This compelling legal basis of the Nine Dash Line will be put to its sternest test yet in 2016. During the first half of the year, an arbitral tribunal in The Hague, constituted under the United Nations Convention on the Law of the Sea (UNCLOS), is due to issue a final ruling on a Filipino protestation that China's maritime claims in the South China Sea based on its Nine Dash Line are contrary to UNCLOS and invalid.

According to the Aquino government in Manila, which unilaterally commenced arbitral proceedings in January 2013, there is no basis for China's claim as UNCLOS comprehensively addresses the scope of entitlements to maritime resources and supersedes any "historic rights" that China might have had in the South China Sea. Further, where the Convention did intend to preserve similar such rights, it had done so expressly. Since there is no such provision in the text which recognizes rights on the scope claimed by China within the Nine Dash Line, the claim should be deemed as invalid.

The accusations leveled against Beijing by the Aquino government are identical to those laid out in a legal study of the Nine Dash Line that was issued by the Obama administration in December 2014. In that study, the US government had additionally claimed that China was not entitled to derogate from the UNCLOS's provisions by claiming "historic rights" under a separate head of general international law. International jurisprudence, too, it noted had supposedly confirmed that such history-based prior usage and related rights which might have existed were now overridden. 

Manila's and Washington's assertion of the invalidity of the Nine Dash Line as a perimeter of the "historic rights" enjoyed by the Chinese people in the South China Sea is legally flawed. Far from being extinguished, recent case law since the entry into force of UNCLOS has decisively come down in favor of the independent existence and preservation by the Convention of such privately-acquired and historically-consolidated rights in foreign exclusive maritime zones.

In a landmark ruling in the late-1990s, the International Court of Justice (ICJ) had authoritatively pronounced that there are special factors, notably traditional fisheries-related factors, that are capable of creating "historic rights" in maritime spaces. These "historic rights" can be exercised non-exclusively by a third state such as China in the exclusive economic zone (EEZ) of a coastal state, in this case the Philippines.

So long as these special factors qualify as giving rise to a local tradition or custom, these "historic rights" are not qualified by the provisions specified in the text of the UNCLOS. Rather, these rights are governed by the rules and principles of general and customary international law and continue to operate.

Subsequent jurisprudence has confirmed that such non-exclusively exercised access rights related to the traditional fishing regime were preserved by the Convention and that it had never been the intent, in the first place, of the drafters of the Convention to interfere with their exercise.

Quite to the contrary, the Convention obligates the coastal state, the Philippines, to respect these historically-acquired rights of a third state, China, in the course of its exercise of jurisdiction within its exclusive maritime zones.      

It is equally erroneous on the part of Manila and Washington to claim that from a procedural standpoint the UNCLOS is comprehensive in scope and that Beijing cannot derogate from the Convention's provisions on such matters by claiming "historic rights" under a separate head of general international law.

The preamble to the UNCLOS explicitly admits that the Convention is not all-encompassing and that such category of other rights that are not regulated by the Convention continue to be governed by the rules and principles of general international law.

 Indeed, in spring 1982, at the time when the Draft Convention of the Third Conference on the Law of the Sea was on the verge of being provisionally adopted, the ICJ had observed that the Convention contained historic rights-related references that were neither defined nor elaborated. As such, these references continued to be governed by the rules of general and customary international law and UNCLOS does not provide any guidance in their regard. 

Further, to assert that UNCLOS only intended to preserve those rights that are explicitly provided for in its textual provisions is to interpret international law backward.

As a matter of legal stability, general principles of international law do not allow such local custom or tradition-based privately-acquired rights to be terminated at will and without reparation, let alone by inference.

Clearly, from a jurisprudential, substantive and procedural point of view, the Nine Dash Line has a firm basis in international law. The Philippines' criticisms to the contrary are unwarranted and lack merit.

China, nevertheless, bears a responsibility to lay out this "historic rights" claim in a more recognizable manner. Its current formulation is ill-defined and vague. Until such time that such a recognizable claim is furnished, the Line will remain a possible "historic rights" line with a putative basis in modern international law.

The author is a resident senior fellow at the Institute for China-America Studies in Washington, D.C. opinion@globaltimes.com.cn