On December 28, 2016, the United States sent a Note Verbale to the People's Republic of China to object China's maritime claims in the South China Sea. This note was a response to documents published by China that are intended to assert their claims in the South China Sea. Then, on June 1, 2020, the United States sent an Official Letter to the United Nations, continuing and emphasizing its objections to China's claims in the South China Sea. In general, the June 1, 2020 official letter was a response to China's Note Verbale CML/14/2019 to the United Nations in protest of Malaysia's submission of the outer limit of its continental shelf. This article focuses on analyzing some of the legal aspects that the United States refers to in the Note Verbale 2016 and the Official Letter 2020 sent to the United Nations. These focus on issues such as: (1) Freedom of navigation in the South China Sea; (2) Island and maritime zone identification on the basis of islands; (3) The legal regime of the low tide elevations. These issues are analyzed on the foundation of the 1982 Law of the Sea Convention and other relevant provisions of international law.