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US-China International Law Disputes in the South China Sea

Wild Blue Yonder --


China’s incremental expansion and bold territorial claims in the South China Sea (SCS) over the past 20 years have raised global concerns. Each year, 3.4 trillion dollars of trade goods are shipped through the SCS, and over 80 percent of crude oil destined for Japan, Taiwan, and South Korea transit this area.1 The US has enforced international law under provisions of the United Nations Convention on the Law of the Sea (UNCLOS) through routine operations in the SCS by US Navy/Coast Guard ships and US Navy/Air Force aircraft Freedom of Navigation (FON) operations. These FON operations have been conducted in disputed waters and airspace, in which the Chinese lay claim to maritime territories represented by its nine-dash line. Since UNCLOS was not ratified by the Senate in 1994, the US enforces international law based on customary international law with respect to China’s violation of UNCLOS and repeated harassment of foreign vessels. Given the US-China tension in the SCS, some have argued that the US should ratify the 1994 agreement to UNCLOS to build legitimacy with partners in the region and apply pressure to China to abide by international law. Others have argued that the US need not ratify UNCLOS since its military FON actions are consistent with UNCLOS and customary international law. This article will examine the history of US support of UNCLOS, China’s nine-dash line claim, and the intersecting issues related to international law and territorial disputes in the SCS.

Figure 1: China Construction at Fiery Cross Reef in the Spratly Islands, (January 28, 2015)37


During the first conference for UNCLOS in 1958, four law of sea conventions, which remain in effect today, were ratified by the US Senate and used to develop what eventually became the 1982 UNCLOS.2 As a lead negotiator with UNCLOS, the US did not ratify this multinational agreement in 1982 due to a controversial seabed floor provision. UNCLOS was later modified in 1994 to address the concerns raised with this provision. Today, 168 countries officially recognize UNCLOS, which defines a coastal nation’s exclusive economic zone (EEZ) as 200 nautical miles from the coast and territorial waters as twelve nautical miles from the coast.3 Since the 1994 UNCLOS modification to seabed claims, the US executive branch has supported UNCLOS, and, currently, the UN maintains a “provisional application” for the US.4 In addition to executive branch support of UNCLOS, every US Chief of Naval Operations since the development of UNCLOS in 1982 has supported ratification.5 Additionally, every Chairman of the Joint Chiefs of Staff has written a letter to the Senate stressing the need for the US to become a party to UNCLOS.6 Since the 1994 update to UNCLOS to address concerns with the original 1982 agreement, every Senate has failed to bring UNCLOS to a vote.7 UNCLOS has repeatedly been blocked by Senate opposition due to concern of reduced US sovereignty and the argument that UNCLOS is not needed since much of it has already been established as customary international law.8

Figure 2: Contested Areas in the South China Sea38

China’s Nine-Dash Line

As a party to UNCLOS, China has sought to invoke its sovereign rights to maritime territory beyond China’s EEZ and claim an area that encompasses nearly the entire SCS.9 China presents its SCS claim as a map that depicts nine-dashes that stretch across the SCS, hence the term nine-dash line. The nine-dash line is a vague representation of what China argues is their historic maritime claim. First presented in 1947 (as the eleven-dash line by the Chinese Nationalist Party, also known as Kuomintang), the nine-dash line depiction of China’s SCS maritime claim provides little detail and lacks defined coordinates for the seemingly arbitrary dashes on the map.10 With no “coherent legal basis,” China did not formally announce its nine-dash line claim to the UN until 2009.11 China’s nine-dash line claim to waters beyond its internationally recognized EEZ encompasses various disputed territories within the Spratly Islands, Paracel Islands, and Scarborough Shoal. From 2014-16, China made further claim to the nine-dash line maritime territory by constructing various artificial features through dredging in the Spratly and Paracel Islands.12 Under UNCLOS provisions, these artificial features do not “strengthen China’s territorial claims as a legal matter” for its justification of the nine-dash line.13

Figure 3: 1947 Kuomintang Eleven-Dash Line / 2009 UN Submitted Nine-Dash Line

US Freedom of Navigation Operations39

Due to China claiming the maritime territory represented by the nine-dash line, the US has increased its FON operations throughout the SCS to enforce international law by operating within China’s nine-dash line.14 The US has been persistent with enforcing UNCLOS provisions in respect to FON in international waters and airspace within the nine-dash line. Although the US never ratified UNCLOS, its increased FON missions are recognized as abiding by customary international law. China claims that the US FON operations are violating international law due to the use of military ships and aircraft. Within the nine-dash line area, China consistently violates UNCLOS through routine harassment of civilian vessels within their respective EEZ. In June 2011, China severed cables to oil exploration vessels from Vietnam as they operated within its EEZ.15 In addition, China collided with a Vietnamese fishing vessel in the vicinity of the Parcel Islands in April of 2020.16 In 2016, a UN tribunal concluded China violated UNCLOS for operating within the Philippines’ EEZ, interfering with fishing and petroleum activity, constructing artificial features, and conducting law enforcement activity that led to near-collisions at sea.17

Given China’s opposition to foreign military operations within its EEZ and nine-dash line, the number of US military incidents and near miss collisions at sea and air has led the US to spearhead agreements between China and the US to prevent a catastrophic event from occurring. The first international airspace incident occurred in 2001 with the collision of an aggressive Chinese fighter with a Navy EP-3E Aires II, and the first international incident at sea involved the harassment of the USNS Impeccable in 2009.18 Both were conducting intelligence, surveillance, and reconnaissance (ISR) FON missions. In 2013, a Chinese navy ship placed itself in the path of a US cruiser forcing the US ship to change course in order to avoid a collision.19 This event led the US to seek a non-binding Code for Unplanned Encounters at Sea (CUES) with Pacific navies (to include China), in an effort to standardize the actions of ships in the event of unplanned encounters.20 CUES has been criticized, however, because it does not address ship behavior nor does it apply to China’s coast guard, other law enforcement ships, and maritime militia.21

Figure 4a: Mischief Reef in the Spratly Islands, (January 24, 2012)40

Figure 4b: Mischief Reef in the Spratly Islands(October 31, 2017)41

US-China International Law Considerations

UNCLOS allows coastal nations to protect resources within their EEZ and provides freedom of the high seas, to include navigation and overflight for foreign vessels and aircraft.22 China argues they have the right to prevent foreign military vessels and aircraft to enter its EEZ; however, this is not what international law dictates. The basis for US FON operations is to assert the right to freedom of navigation and overflight in China’s internationally recognized EEZ and self-recognized territorial and EEZ claims. The principles of FON have been in existence for 400 years, and the US has continuously used its military to enforce FON throughout its more than 200-year existence.23 US FON operations work to “preserve for all States the legal balance of interests established in customary international law as reflected in the Law of the Sea Convention.”24

China attempts to legally justify the nine-dash line claims through domestic legislation passed in 1992 and 1998. China’s 1992 Law on Territorial Sea and Contiguous Zone claim various disputed islands throughout the SCS as sovereign to China.25 The 1998 Law of the People’s Republic of China on EEZ and Continental Shelf states China’s EEZ applies to all Chinese territorial rights to include the historical rights to the areas defined by the nine-dash line.26 China’s legal basis to argue its rights to the nine-dash line territory is based on Chinese domestic law, not international law.27

With no such provision in UNCLOS, China asserts that UNCLOS limits foreign militaries from operating in its recognized and claimed EEZ.28 With regard to regulating foreign military operations within its EEZ, China is not the only country that makes this assertion. Others, such as Algeria, Ecuador, Iran, Malaysia, Pakistan, and Uruguay hold this same position.29 UNCLOS does claim that coastal nations have the authority over scientific research within its EEZ.30 Through domestic law, China passed the 2002 Surveying and Mapping Law of the People’s Republic of China that broadly defined research activities and made the argument that military platforms conducting ISR be considered scientific research.31 Combining the UNCLOS provision that allows nations to control scientific research within its EEZ and claiming military ISR as scientific research, China argues it should control foreign military activity in its internationally recognized/unrecognized EEZ. The Chinese again use domestic law in combination with international law to justify its actions towards preventing the US from conducting FON operations within its EEZ and self-recognized nine-dash line territories.

China’s interpretation of international law is that the movement of military ships should be restricted inside China’s EEZ.32 China also attempts to make the distinction between ‘navigation’ and ‘passage’ with regard to military operations through China’s EEZ.33 China claims it has no problem with the ‘passage’ of military vessels/aircraft, but when these units perform ISR with ‘navigation’ it is violating international law, which is contrary to international norms in respect to FON. This claim is also inconsistent with China’s routine harassment of foreign civilian vessels within the disputed maritime territories of the nine-dash line area.

Figure 5: China’s Claimed Territorial Waters and UNCLOS Recognized Exclusive Economic Zones in the South China Sea42


Because it is not a party to UNCLOS, the US lacks the ability to bring international maritime disputes to the UN.34 The US Navy and Coast Guard have also asserted that securing cooperation with partners in the region is complicated due to the non-party status of the US.35 It has been argued that by becoming a party to UNCLOS, the US could shape its provisions and exert more influence among China’s neighbors who are affected by China’s nine-dash line claim, potentially constraining China’s territorial expansion.36 Continuing not to ratify this convention, some assert, could negatively impact the credibility of the US to enforce international law and may influence China’s boldness to continue to stake claims in disputed territories throughout the SCS.

China has ratified UNCLOS although it rejects some of its binding provisions, while the US has not ratified UNCLOS although it enforces certain provisions through its FON operations. Although not a party to UNCLOS, the US consistently disputes China’s EEZ and nine-dash line claims through FON operations asserting rights of customary international law. Through these actions, the US has demonstrated that it supports elements of UNCLOS. Considering the historical precedence set by customary international law, it seems to be irrelevant whether or not the US ratifies UNCLOS. To promote freedom of the seas in the SCS, the US and its allies will likely continue FON operations in an ongoing effort to contest China’s unsubstantiated claims.

Commander Jon Marek, USN

CDR Jon Marek is a US Navy reservist assigned to the Air War College, Air University, Maxwell AFB, Alabama. He has a background in air anti-submarine warfare, anti-surface warfare, and reconnaissance.
This paper was written as part of an Air War College elective, Select Topics in National Security Law.


1 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas: Background and Issues for Congress,” Congressional Research Service, Report: R42784, Version 114, 28 August 2020, 6.

2 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 48.

3 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 48.

4 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 49.

5 Scott Truver, “UNCLOS MythBusters,” US Naval Institute Proceedings, Vol 133/7, July 2007,

6 Geoffrey Corn, et al., National Security Law: Principles and Policy, (New York, NY: Wolters Kluwer, 2015), 134.

7 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 49.

8 Stewart Patrick, “(Almost) Everyone Agrees: The US Should Ratify the Law of the Sea Treaty,” The Atlantic, 10 June 2012,

9 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 38.

10 Stefan Halper, “China: The Three Warfares,” For Andy Marshall Director of the Secretary of Defense, (Washington D.C., May 2013), 54.

11 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 15.

12 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 65.

13 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 65.

14 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 49.

15 Stefan Halper, “China: The Three Warfares,” 54.

16 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 17.

17 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 58-59.

18 CDR Bradley May, “The US Senate Should Ratify UNCLOS,” US Naval Institute Proceedings, Vol 138/6, June 2012,

19 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 41.

20 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 52.

21 Ronald O’Rourke, “U.S.-China Strategic Competition in South and East China Seas,” 52.

22 CDR Bradley May, “The US Senate Should Ratify UNCLOS.”

23 CDR Bradley May, “The US Senate Should Ratify UNCLOS,” 4.

24 “Department of Defense Report to Congress: Annual Freedom of Navigation Report Fiscal Year 2020,” Department of Defense, 27 January 2021, 2.

25 Stefan Halper, “China: The Three Warfares,” 62.

26 Stefan Halper, “China: The Three Warfares,” 63.

27 Stefan Halper, “China: The Three Warfares,” 63.

28 CDR Bradley May, “The US Senate Should Ratify UNCLOS.”

29 “Department of Defense Report to Congress,” 4-6.

30 CDR Bradley May, “The US Senate Should Ratify UNCLOS.”

31 CDR Bradley May, “The US Senate Should Ratify UNCLOS.”

32 Stefan Halper, “China: The Three Warfares,” 64.

33 Stefan Halper, “China: The Three Warfares,” 64.

34 Stewart Patrick, “(Almost) Everyone Agrees.”

35 Stewart Patrick, “(Almost) Everyone Agrees.”

36 CDR Bradley May, “The US Senate Should Ratify UNCLOS.”

37 Antonio Carpio, “The South China Sea Dispute,” Library of Congress, Call number: KZA1692, 2017.

38 Ben Dolven, Susan Lawrence, and Ronald O’Rourke, “South China Sea Disputes: Background and US Policy,” Congressional Research Service, Report: IFI0607, 23 February 2017.

39 Antonio Carpio, “The South China Sea Dispute,” Library of Congress, Report: KZA1692, 2017.

40 “Asia Maritime Transparency Initiative,” Center for Strategic International Studies, (Washington, DC),

41 “Asia Maritime Transparency Initiative,” Center for Strategic International Studies, (Washington, DC),

42 Dato Muthiah Alagappa, PhD, “Rethinking Territorial Disputes in South China Sea: Transforming Problem into Opportunity – Analysis,” S. Rajaratnam School of International Studies, 10 September 2012.

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