Taxing power is unlimited---the Supreme Court will overrule any obstacles.
Yonah ’21 [Reuven Avi and Yoseph Edrey; January 22; Irwin I. Cohn Professor of Law and Director of the International Tax LLM Program at the University of Michigan Law School, PhD in History from Harvard University, AM in History from Harvard University, JD from Harvard Law School; Professor of Law at the University of Haifa, PhD in Law from The Hebrew University of Jerusalem, LLM from The Hebrew University of Jerusalem; Law and Economics Working Papers, “Constitutional Review of Federal Tax Legislation,” no. 175]
The Constitution itself imposes very few limits on the taxing power, Unless it is clear that it is not possible to impose taxes that are not intended to pay the Debts and provide for the Common Defense and General Welfare of the United States ”. Goods exported from a State may not be taxed.17 Direct taxes must be apportioned among the states by population18 and indirect taxes must be uniform.19 The only significantly disputed item is the definition of “direct” tax, which in Pollock (1895) led to the Court striking down the second US income tax as unconstitutional, but this decision was reversed by the adoption of the Sixteenth Amendment in 1913.20 There is still some debate among scholars about whether an unapportioned federal wealth tax would be constitutional.21
Nor has the Supreme Court22 imposed significant limits on the power of Congress under the Taxing Clause. The Court has emphasized the sweeping character of this power by saying from time to time that it “reaches every subject,”23 that it is “exhaustive”24 or that it “embraces every conceivable power of taxation.”25 The few subject matter limitations imposed in the past have been overruled.26 Most strikingly, since 1920 the Court has refused to rule any federal income tax statute unconstitutional.27