Details of the ruling
A tribunal ruled that China has no legal basis for its vast claims in the South China Sea and had aggravated the seething regional dispute with its extensive construction of artificial islands that destroyed coral reefs and infringed on the Philippines’ exclusive economic zone.

Besides, the court slammed China for damaging parts of the ecosystem in the Spratly islands — a contested archipelago– on account of overfishing and development of artificial islands.

Who has refferd the matter?
The Philippines, under a U.N. treaty governing the seas, asked in 2013 for arbitration. The five-member panel from the Permanent Court of Arbitration in The Hague, Netherlands, unanimously concluded that China had violated its obligations to refrain from aggravating the dispute while the settlement process was under way. 

About South China Sea dispute
Spartly and Parcel Islands in South China Sea are claimed by six nations namely China, Philippines, Vietnam, Malaysia, Brunei and Taiwan. 

As per United Nations Convention on Law of Seas (UNCLOS),  ownership of islands leads to claim 200 nautical mile  of sea waters adjoining islands. 

Significance of disputed waters
1. Estimated $5 trillion in global trade passes each year.
2. Nearly 3 million sq/ km. of water is under threat.
3. 190 trillion cu feet gas
4. 11 billion barrel of oil reserves

Response of China to ruling
The Chinese Foreign Ministry strongly asserted that Beijing’s "territorial sovereignty and maritime rights and interests in the South China Sea shall under no circumstances be affected by those awards.
The Chinese response follows the ruling by the 5-member international tribunal, which rejected the legal validity of the nine-dash line—the demarcation line underlying Beijing’s claim to most of the South China