CONTRACT LAW

Legally binding means Something is binding legally ( In eyes of court ) . And If It is opposed or performance not undertaken in accordance with it. You can resort to court. For example, A contract is always legally binding. And If either party seller or buyer doesn't perform their part of contract (i.e buyer doesn't accept goods ordered) also called breach of contract. Then The injured party may resort to court for compensation.

If something is legally binding, then the courts can intervene and compel the parties to perform the contract ie force the parties to perform their obligations. I hope this helps clarify :)