Which of these international organization bases it's membership solely on cultural identification

UNESCO (the United Nations Educational, Scientific, and Cultural Organization), founded in the year 1946, is devoted to promote peace and security across the world based on culture, education, and science. It has made declarations agains racism, defended human rights, and stimulated communication, and has also worked to protect the natural and cultural heritage at world level. Thus, while it acknowledges cultural diversity, also seeks to bring union in what the various cultures of the world have in common. It also works to protect the natual environment globally.

it was certainly a debatable decision, mainly because it was based primarily on political - and not on legal or social - views. since the congress at that time was led by members of the republican party, and the territory that the tribes wanted to turn into an exclusively indian state was predominantly democratic, the proposal (as expressed in the constitution) did not succeed, but the constitution itself proved to be of crucial importance in the creation of the state of oklahoma, and, most importantly, it guaranteed the involvement of representatives of the indian tribes in the government of the future joint state.  

as a member of congress, i would have voted to ratify the constitution, or at least to have it tabled. ignoring it was an interested and partial decision.