Judges at an arbitration tribunal in The Hague on Tuesday rejected China's claims to economic rights across large swathes of the South China Sea in a ruling that will be claimed as a victory by the Philippines.
"There was no legal basis for China to claim historic rights to resources within the sea areas falling within the 'nine-dash line'," the court said, referring to a demarcation line on a 1947 map of the sea, which is rich in energy, mineral and fishing resources.
In the 497-page ruling, judges also found that Chinese law enforcement patrols had risked colliding with Philippine fishing vessels in parts of the sea and caused irreparable damage to coral reefs with construction work.
China, which boycotted the case brought by the Philippines, has said it will not be bound by any ruling.
In reaction, China said: "The arbitration tribunal made the illegal and invalid so-called final verdict on the South China Sea dispute on July 12. Regarding this issue, China has made the statement for many times that it is against the international law that the Aquino III administration of Philippines unilaterally requested the arbitration. The arbitration tribunal has no jurisdiction on this matter."
Manila had contested China's expansive territorial claims in the South China Sea, which the Philippines contends are invalid under international law.
This is the first time a South China Sea territorial dispute has been brought to the Permanent Court of Arbitration (PCA) in The Hague and many think it will rule in favor of the Southeast Asian nation.
Control of the region is valuable because more than $5 trillion worth of global trade passes through the South China Sea each year, and China has been accused of ramping up tensions over control in recent years by building artificial islands on reefs, on which it has added airstrips and other military-style installations.
The U.S. is seeking to maintain "freedom of navigation" in the region for its ships including military vessels.
The case is under scrutiny globally as it could change the region's geopolitical landscape and set future precedence for similar challenges.
In China, the guns were out on Weibo where #SouthChinaSeaArbitration was a top trending topic on the Twitter-like social media platform on Tuesday.
Rumor (who attached this graphic with the nine dash line):
"Vow to protect the complete territorial integrity of the People's Republic of China! This is our China!"