So, you are implying that a non governmental organization like the World Health Organization could somehow overcome the power of locals governments and sovereign countries. I do not think it should work like that.
As far as I understand, that organization is supposed to offer recommendations and protocols the countries worldwide are supposed to choose if it is suitable for populations.
If the WHO was some kind of entity which was able to govern over presidents and prime ministers, there would not be people and entire communities doing things which are disapproved by them, like in Africa with all the folk medicine.
Country and local governments are made up of people, some of whom want complete control. The Covid scare has given more governments more control than any other operation, ever. So, by agreement of government leaders - who are misusing their authority - and by election from these government people, the WHO has been given authority.
The agreements are rather secretive. But they are being brought out into the open so that the people will think that they must obey, because their government authorized it.
More than any other countries in the world, it is written right into the laws of the US, Britain, Canada, and Australia - common law - that the people have control over their governments. The trouble is that the people don't know how to use their control. Often they attempt to use it the wrong way. If they don't figure out how, their countries' laws might be changed so that they lose their authority.
Everything is done by agreement. A government doesn't get set in place without agreements of and between people. Same with the WHO being set in authority.
Consider a simple hostage situation... one captor and one hostage. The captor says to the hostage, "Do what I tell you, or I will shoot you dead." The hostage either lives or dies by agreement with the captor. Maybe the captor was lying. Or maybe his gun didn't have any bullets. Even then, the whole thing was settled by agreement.