Please be aware that the IRS emphasizes to taxpayers, promoters, and return preparers that there is no right to exemption from federal income tax for Native Americans under an unspecified “Native American Treaty.” Any return position based on an unspecified “Native American Treaty” has no merit and is frivolous. As a general rule, Native Americans are subject to federal income tax just like every other American. see for reference - http://www.irs.gov/irb/2006-15_IRB/ar09.html
Please see examples provided by the IRS.
Similar situation is with possible state income tax liability.
Let me know if you need any help.