Legal Justification for China not following decision in Philippines v. China

Question

An award was given by the Permanent Court of Arbitration in the case The Republic of the Philippines v. The People’s Republic of China. However, as I knowledge tells me, except internet domain name disputes, all arbitration requires both parties to be agree on the dispute to be resolved by the arbitration tribunal. Therefore, my question comes:

Are China not legally required to follow that decision as China did not agreed to put this case in the court? Or are there any conventions force China to follow that decision?

**I am not really familiar with Public International Law, so please tell me if I have made any mistakes in my question.

Answer 1

The Permanent Court of Arbitration is a bit confusing, but essentially, it's an arbitrator rather than a court. The primary reason for this is that it deals with sovereign states, which recognise no higher authority.

Like all arbitration, the parties agree to the arbitrator's decision being binding prior to entering into arbitration.

If this were a matter between private parties, breach of the agreement following an unfavourable decision could be enforced by a court of competent jurisdiction.

However, when dealing with sovereign states, a breach of the agreement is somewhat more complicated; there is no court that can compel performance under the agreement.

That leaves the aggrieved state with a number of means of redress, which may be economical (trade embargoes), military (declaring war), or something else... maybe diplomatic, such as withdrawing ambassadorial privileges and the ability for the other state's nationals to enter territory.

Of course, this is vastly more complicated than the scope of an answer on this site; the legal answer is that the Permanent Court of Arbitration is not a court, it has no power to and does not enforce its rulings (and the International Court of Justice is in a similar position anyway).