WHO can declare world pandemic and declare any vaccination mandatory in 194 countries. Those 194 countries connected to WHO can have their governments suspended by WHO who can place a emergency non elected government and take over the country.
This emergency government responds only to WHO and EU (in Europe) and to the UN (in USA and the rest of the world).
Their limitations are not an issue, since there are no limitation concerning a real or fake health crisis. If they can take over 194 countries they can do whatever they want.