What part of 'constitutive document of the united nations' or 'forms part of customary international law' or 'foundation of two BINDING un human rights covenant' don't you understand, hmmm?
As interpreted by you. Even the UN says GA resolutions are not legally binding. At best you can make the case that it will become customary law, but how many countries ignore this? Tons.
More to the point, what sort of sovereign nation affixes its consent on the udhr, uses the principles therein to apply diplomatic pressure on other nations and yet REFUSES TO APPLY IT WITHIN ITS OWN DOMAIN????
Uhm, China does, Saudi Arabia does, Iran does, Russia does. You do not seem to grasp how international politics actually works.
The udhr is the guideline by which states and governments are OBLIGED to comport themselves. And sovereign nations comport themselves through law. It represents the culmination of the logical principles of political philosophy started in ancient greece.
You say they are obligated to follow it and I point out there is no enforcement mechanism and countless countries violate its principles daily. If you cannot enforce an obligation, then it is not a real obligation.
What can be more powerful than logic stated as a UNIVERSAL LAW, hmmm?
If you ask me there are very few universal natural laws, and a declaration of human rights that is roundly ignored does not fit into this category.