Chinese law enforcement activities in its own territorial waters legitimate and justifiable

In January 2013, the Philippines unilaterally instituted arbitration proceedings against China with respect to its disputes with China in the South China Sea. On March 30, 2014, the Philippines presented a Memorial consisting of 15 Submissions. In Submission 13, the Philippines complained about two series of allegedly dangerous actions conducted by China's law enforcement vessels against Philippine law enforcement vessels on April 28 and May 26, 2012. The Philippines alleged that China thus violated relevant provisions of the Convention on the International Regulations for Preventing Collisions at Sea (COLREGs), and the UN Convention on the Law of the Sea (UNCLOS).

To support its allegations, the Philippines retained Professor Craig H. Allen of the University of Washington, who presented his written opinion to the arbitration tribunal at the Permanent Court of Arbitration in The Hague on March 19, 2014, and Professor Alan E. Boyle of Essex Court Chambers of the United Kingdom, who gave a statement before the tribunal on behalf of the Philippines on Nov 26, 2015.

The argument of Boyle and Allen was: China's law enforcement vessels, by approaching Philippine vessels at close range rather than keeping well clear, violated the COLREGs; China thereby violated Article 94 of UNCLOS as a flag state for failing to exercise effective jurisdiction and control over its vessels.