An international tribunal in The Hague released a landmark decision on Tuesday in a dispute between China and the Philippines over the South China Sea. Here are answers to six questions about the case.

What is this case about?

The Philippines filed a complaint in 2013 after China took control of a reef about 140 miles from the Philippine coast. It accused China of violating international law by interfering with fishing, endangering ships and failing to protect the marine environment at the reef, known as Scarborough Shoal.

But the Philippines also went further, asking an international tribunal to reject China’s claim to sovereignty over waters within a “nine-dash line” that appears on official Chinese maps. The dashes encircle as much as 90 percent of the South China Sea, an area the size of Mexico that is vital to global trade and rich in natural resources, including potential oil deposits.