On Monday, the United States challenged China for its territorial expansion into maritime waters, as two U.S. Navy guided missile destoyers sailed close to reefs occupied by China. ABC News reported, “The USS Preble and USS Chung Hoon traveled within 12 nautical miles of the Gaven and Johnson Reefs in what the Navy calls a freedom of navigation operation ‘in order to challenge excessive maritime claims and preserve access to the waterways as governed by international law,’ said Seventh Fleet spokesperson Cmdr. Clay Doss.”
Reuters noted, “The busy waterway is one of a growing number of flashpoints in the U.S.-China relationship, which also include a trade war, U.S. sanctions and Taiwan. President Donald Trump dramatically increased pressure on China to reach a trade deal by threatening to hike U.S. tariffs on $200 billion worth of Chinese goods this week and soon target hundreds of billions more.”
Seventh Fleet spokesperson Cmdr. Clay Doss stated, "All operations are designed in accordance with international law and demonstrate that the United States will fly, sail and operate wherever international law allows. That is true in the South China Sea as in other places around the globe.”
Reuters stated that Chinese foreign ministry spokesman Geng Shuang said the U.S. ships did not have permission from the Chinese government and the Chinese navy warned them to leave. Shuang added, “The relevant moves by the U.S. ships infringed upon Chinese sovereignty, and damaged the peace, security and good order of the relevant seas. China is strongly dissatisfied with this and resolutely opposed to it.”
China says it owns virtually all of the South China Sea despite the claims of territoriality from Brunei, Indonesia, Malaysia, the Philippines, Taiwan and Vietnam.
The South China Morning Post explained, "China claims more than 80 per cent, while Vietnam claims sovereignty over the Paracel Islands and the Spratly Islands. The Philippines asserts ownership of the Spratly archipelago and the Scarborough Shoal, while Brunei and Malaysia have claimed sovereignty over southern parts of the sea and some of Spratly Islands … China's 'nine-dash line' is a geographical marker used to assert its claim. It stretches as far as 2,000km from the Chinese mainland, reaching waters close to Indonesia and Malaysia … One third of global shipping, or a total of US$3.37 trillion of international trade, passes through the South China Sea."
The United States has argued against China constructing military installations on artificial islands and reefs. The Voice of America reported in 2016:
Many nations have urged Beijing to abide by the United Nations Convention on the Law of the Sea (UNCLOS), which sets maritime zones of control based on coastlines. The United States, which has signed onto UNCLOS without ratifying it, often relies on the international agreement to settle territorial disputes. China has refrained, invoking intertemporal laws based on the deep historical record, such as archaeological findings on disputed reefs and islands. At best, China views U.N.-backed codes of maritime governance as incompatible with domestic laws; at worst, it sees them as instruments of Western hegemony designed to undercut its expanding influence as a world power …
In July, a five-judge panel in The Hague unanimously rejected the legal basis of nearly all of China’s maritime claims. Within weeks, China’s Supreme People’s Court issued a regulation stating a “clear legal basis for China to safeguard maritime order,” in which Beijing vowed to prosecute any foreigners found fishing or prospecting in disputed waters.