There is a very simple answer to this question and that is, "Yes, IF the tribe is paying federal taxes they can claim the WOTC credit." In addition, they would qualify for the Indian Employment Credit which is another Hiring Incentive that we screen for.
Below is some additional information that can be found in the:
OVERVIEW OF FEDERAL TAX PROVISIONS RELATING TO NATIVE AMERICAN TRIBES AND THEIR MEMBERS
From the Public Hearing Before the SENATE COMMITTEE ON FINANCE on July 22, 2008
As sovereign entities, tribal governments are completely exempt from federal taxation. Tribal governments can form business corporations that also are exempt from income taxes. According to a 2012 article in "Forbes" magazine, in 2012, Native American tribes operated 422 gaming facilities on tribal lands and didn't have to pay taxes on their earnings. However, individual Native Americans are also U.S. citizens and must pay federal income tax. Therefore, when tribal income is distributed to individuals, they must report it as taxable income.
Federal tax treatment of income from gaming operations. As is discussed above, Indian tribes and wholly owned tribal corporations chartered under Federal law generally are not subject to income tax. Therefore, gaming income of such tribes or tribal corporations generally is not taxable.
A tribal corporation incorporated under State law may, however, may be subject to tax on such income. Under certain circumstances, the IGRA permits Indian tribes to make per capita distributions to members from revenue derive d from certain gaming activities conducted or licensed by the tribe. The IGRA explicitly subjects the receipt of such distributions to Federal income tax.48 Such distributions also are subject to special withholding requirements.