Why are clients under J-1 teacher treaty provisions filing a 1040NR charged AMT on the non-exempt source income earned after they pass their 2 year exclusion period?fter the

[Nogales Tax Pro]

I have researched this matter considerably and can only find infomation in the IRS and other publications about AMT being calculated for non-residents who receive foreign tax credits.  I cannot find any reference to clients under J-1 teacher treaty terms being charged AMT tax on they earnings they received in a calendar year in which they were partially allowed tax exemptions and partially subject to tax after they had passed their two year exemption period. I do see that non-source income for non-residents is calculated at a flat 30% and that source income is subject to normal tax withholding. Please direct me to the law or statute which states that such individuals are subject to AMT on their non-exempt earned income.