Since at least the 15th century, Indigenous peoples' homelands have been invaded and occupied by European colonizers, who initially justified colonization under the authority of the Catholic Church to spread Christianity through the Doctrine of Discovery. Thousands of indigenous nations throughout the world remain occupied by about two hundred political constructs known as states which formed as a result of colonialism. Indigenous peoples continue to face threats to their sovereignty, economic well-being, languages, ways of knowing, and access to the resources on which their cultures depend. Indigenous rights have been set forth in international law by the United Nations, the International Labour Organization, and the World Bank. In 2007, the UN issued a Declaration on the Rights of Indigenous Peoples (UNDRIP) to guide member-state national policies to the collective rights of Indigenous peoples, including culture, identity, language and access to employment, health, quality education and natural resources.