Tribal governments are governments that have standing agreements with the United States on a federal level. They are their own independent entities, and they are not required to have a Tax ID/EIN. They do not need to pay excise taxes the way that US companies would need to, and consequently they don’t need to file US tax returns, or follow US hiring procedures.
There is one catch: If an entity within the Indian tribal government hired employees from the United States, they may be required to get an EIN. The Indian tribal government would still need to pay taxes for US employees, and consequently would need employer identification numbers, and would need to collect W2 forms for the employees. But other than this requirement, a tribal government should not be required to have a tax ID. In fact, few businesses are required to have an EIN; it’s simply that actions businesses take (such as opening a business bank account, or paying business taxes) require them.