スカボロー礁
The 2012 Scarborough Shoal standoff between China and the Philippines led to a situation where access to the shoal was restricted by the People's Republic of China. The expected intervention of the United States to protect its ally through an existing mutual defence treaty did not commence after the United States indirectly stated that it does not recognise any nation's sovereignty over Scarborough Shoal, leading to strained ties between the Philippines and the United States. In January 2013, the Philippines formally initiated arbitration proceedings against China's claim on the territories within the "nine-dash line" that includes Spratly Islands and Scarborough Shoal, which it said is "unlawful" under the United Nations Convention on the Law of the Sea (UNCLOS). An arbitration tribunal was constituted under Annex VII of UNCLOS and it was decided in July 2013 that the Permanent Court of Arbitration (PCA) would function as registry and provide administrative duties in the proceedings.