They only declared that? What more could have been done? The declaration that was made was the main treaty of the Allies and eventually became the founding charter for the UN, which most countries in the world are a member of and have ratified in their own laws.
It's a bit tongue in cheek, but maybe avoid the red witch hunts, avoid murdering your own population for being black or revolutionary (or both). And for the French and British, not executing colonial soldiers and their families to avoid paying them (or to avoid respecting your promises of Freedom(tm) )
Maybe it was just a troll, but implementation is clearly not finished yet, and was surely not at the end of the war.
