there are number of international conventions that create the international network for protecting Human rights. in this regard, how international aw can possibly bind the IOs.
When there exist problems that affect entire regions such as the forced migration due to hyperinflation in Venezuela. Nearby countries are affected Dear Prof.
In a world of diffused powers, no sovereign country is obliged by any external law. However, countries take part in global initiatives. One fine example is Earth Summit (1992) and its three conventions.
I, personally, like the analogy used by the director of UN Sustainable Development Solutions Network (UNSDSN). UN SDGs (in general, any global initiative signed by a participating nation) are the "music-sheet" in a conductor-less orchestra. There is no conductor who directs the nations. They all follow their music sheets and coordinate based on gauging each other.
Coming back to the question:
When: Only when a country has signed an agreement/resolution/etc.