This summer was a very important period in the history of U.S. involvement in the South China Sea. For the first time since 2010, a senior government official used blunt language to publicly accuse Beijing of making unlawful maritime claims, and Washington finally began punishing companies that assist in China’s illegal island building.

On July 13, Secretary of State Mike Pompeo announced a significant strengthening of U.S. policy regarding China's claims in the South China Sea. He said the U.S. was aligning its position to match the July 2016 decision by the Hague Arbitral Tribunal finding, a legally binding award that rejected the PRC's expansive maritime claims in the South China Sea. Specifically, Pompeo indicated China has no lawful maritime claim over waters determined by the tribunal to be inside the exclusive economic zone (EEZ) of the Philippines or on its continental shelf. He called Beijing's harassment of Philippine fishing and offshore energy development activities "unlawful" and went on to identify other examples of China's illegal claims:

United States rejects any PRC claim to waters beyond a 12-nautical mile territorial sea derived from islands it claims in the Spratly Islands…. As such, the United States rejects any PRC maritime claim in the waters surrounding Vanguard Bank (off Vietnam), Luconia Shoals (off Malaysia), waters in Brunei’s EEZ, and Natuna Besar (off Indonesia). Any PRC action to harass other states’ fishing or hydrocarbon development in these waters — or to carry out such activities unilaterally — is unlawful.

This statement was followed the next day by a forceful speech in which Assistant Secretary of State David Stilwell accused China of "gangster tactics" in the South China Sea. Why did all of this happen? Seemingly, this new policy approach had been in the works for some time, but it was rolled out this summer because of blatantly aggressive Chinese activity in the South China Sea early this year, coupled with a series of gross misrepresentations of international law as it applies to the South China Sea made by Beijing in the United Nations.

What did Washington hope to accomplish? First, it was throwing its weight behind the claims of its Southeast Asian allies and partners in upholding their legitimate sovereign rights created by the United Nations Convention on the Law of the Sea (UNCLOS). These rights were reaffirmed and clarified by the July 2016 tribunal findings — and were being dismissed by China in the UN.

The second objective was to clarify that the United States does take sides on maritime claims. Too often over the past ten years, Washington failed to differentiate between the policy of taking no position on “sovereignty claims” versus taking a position on illegal claims to maritime rights. Pompeo’s policy statement is not about who has sovereignty over the approximately 180 named islands, rocks, shoals, sandbanks, reefs and cays above water at high tide in the South China Sea. It is about water and ocean resources. The long-held U.S. policy of not taking sides in sovereignty disputes over the land features remains in place. In short, the PRC should stop trying to assume jurisdiction over waters that do not belong to them.

In practice, Pompeo’s statement also means the United States does not support China’s claims to “historical rights” to the fish, hydrocarbons, and other resources in the South China Sea; a claim Beijing officially announced in July 2016. Unfortunately for China, the arbitral tribunal found the country had no such historical rights. Even if they ever had any, which the panel doubted, they were surrendered when Beijing signed the UNCLOS treaty. In short, China’s “historical rights” claim was illegal, because, among other things, it grossly infringed on the exclusive economic zones of Vietnam, Malaysia, Indonesia, Brunei and the Philippines. China ignores this legal inconvenience and uses its coast guard and maritime militia to bully its South China Sea neighbors whenever they attempt to harvest the ocean resources that international law assigns to them. While China has not said so explicitly, its heavy-handed practices make clear it believes its historical rights claim applies to the water area inside of the so-called “nine-dash line,” a U-shaped curve drawn on Chinese nautical charts.

The third objective was to clarify that while Washington takes no sides on sovereignty disputes over land that can be claimed, it does take a position on sovereignty claims over areas that no country can lawfully claim. Specifically, Beijing claims sovereignty over underwater features such as Macclesfield Bank or James Shoal that are submerged even at low tide. This is illegal. It is also illegal to claim —“to appropriate,” in the language of the UNCLOS treaty — features that are above water only at low tide. China has claimed and occupied such “low-tide elevations,” even building large bases on Subi and Mischief Reefs. UNCLOS expressly prohibits such appropriation, and states that low tide elevations possess no territorial sea or EEZ.

A fourth objective was to adopt as its own the Obama administration’s hard line against military base development on Scarborough Shoal. In early 2016, Scarborough Shoal suddenly became a new issue of serious concern for U.S. officials, because information strongly suggested the People’s Liberation Army was making plans to turn the 150-square-kilometer shoal and lagoon into another artificial island, similar to their earlier island-building in the Spratlys. Whether this was China’s intent is uncertain, but Obama administration officials reacted as though they thought it was and mounted a full-court press aimed at dissuading Beijing from developing Scarborough. A small task force of U.S. Air Force tactical aircraft was rotationally deployed to the Philippines, and USS John Stennis Carrier Strike Group conducted presence operations in the South China Sea for much of March, April and May of 2016. The Pompeo and Stilwell statements make clear that the Trump administration also recognizes the destabilizing impact of any attempt to turn Scarborough into an air-capable base. In response to a question, Stilwell made it clear that if China were to physically occupy, reclaim or militarize Scarborough, Washington would consider that a very dangerous step, with lasting and severe consequences for Beijing’s relationship with Washington.

Finally, in the category of “better late than never,” for the first time Washington employed coercive measures in response to Beijing’s sustained, illegal South China Sea activities. In late August, 24 Chinese companies that were involved in building island bases in the South China Sea during both the Obama and Trump administrations were placed on the so-called “entity list,” prohibiting them from buying U.S. technology or other products. The government also announced U.S. visa restrictions on Chinese individuals associated with these firms.

In conclusion, these recent steps have been a necessary clarification n of U.S. policy in response to Chinese behavior in the South China Sea. But Beijing still has a great deal of unfinished business in the South China Sea. China is not alone in the Spratly Islands; it still believes it has get the Filipinos, Vietnamese and Malaysians off the 40 or so features they occupy in the Spratlys — without starting a war. It still wants to exploit the resources of the Philippines’ Reed Bank. It still wants to turn Scarborough Shoal into a base so it can complete a network of air bases to control all of the South China Sea airspace in times of conflict. Finally, it hopes to persuade the government of the Philippines to cancel the Enhanced Defense Cooperation Agreement with the United States in order to diminish the prospect of U.S. air power returning to the Philippines. These Chinese ambitions raise unanswered questions. Most importantly, what actions — if any — will the United States take, should Beijing continue to “slap around” its South China Sea neighbors, ignoring Washington’s diplomatic and economic interventions?

Rear Adm. Michael McDevitt focuses on U.S. security issues in East Asia. He founded CNA's Strategic Studies division in 2000, and since stepping down as a Vice President in 2012 has been active as a Senior Fellow, leading several major projects related to maritime disputes in the East and South China Seas and China's ambition to become a "great" maritime power.