Beijing gave up its rights to the South China Sea after signing up to a United Nations convention, a former U.S. Defense Secretary said Wednesday, a day after an international tribunal ruled that China's claims of historical rights over the disputed waters were not founded on evidence.

A tribunal at the Permanent Court of Arbitration in The Hague, Netherlands, decided on Tuesday that China's claims to the disputed waters were counter to international law.

The Philippines had contested China's expansive territorial claims in the South China Sea, which Manila contended were invalid under international law.

China, however, said its historic rights predated the United Nations Convention on the Law of the Sea (UNCLOS) and were not at odds with the provisions of the treaty , to which both countries were signatories.

But the East Asian giant relinquished those rights when it signed the UNCLOS, former U.S. Secretary of Defense, Chuck Hagel said.

"(It) explicitly states in that treaty and when you sign that treaty, you would and do relinquish all previous historical rights to any contested territory. So China essentially put itself in this position to be part of whatever the international tribunal comes down with," Hagel told CNBC's "Squawk Box".

"(The tribunal) is one of the most important post World War II institutions that has been set up to try to bring some order to a world that had gone without any order which lead to two world wars. I think it's important that we continue not only to maintain, but to support the force of those international tribunals," he added.

The Philippines wasn't the only big winner in a legal decision on rights to the resource-rich South China Sea, according to experts.

Malaysia, Vietnam and Indonesia are also set to benefit from the ruling, which dealt a painful blow to China's national pride

The Hague found the so-called 'nine-dash line' — a rough demarcation that China uses to set out what it believes is its territory—was illegal when applied to the Philippines, that meant it was also illegal when applied to other countries, added Paul Reichler, a partner at Foley Hoag and lead lawyer for the Philippines in the case.

"They are big winners as well," Reichler told CNBC's "The Rundown."