SCOTUS has correctly ruled that the only effect of the 16th Amendment was to define the income tax as not being a "direct tax," which necessarily means that it is an indirect tax, and so is subject to the Constitutional constraints on indirect taxes.
Unfortunately, SCOTUS has incorrectly interpreted the semantics of the uniformity requirement. But the requirement clearly and unambiguously requires that the tax itself, not the law that imposes it, must be "uniform." Progressive rates violate that constraint.
Sorry for the repost in post #35.
The legal argument for uniformity is flawed. Within each income tax bracket, the tax rate is indeed uniform. Since the income tax is confined to ‘income’ however defined, the federal government has had a free hand to draw income brackets however it wishes, and as just said, the tax rate is applied uniformly with each tax bracket.
The law is vague and allows for a backdoor progressive income tax.
The FairTax code http://www.fairtax.org has the NRST that is uniformly applied as a nondirect excise tax on RETAIL consumption. It abolishes the Income tax code in toto. It does not repeal the 16th amendment and sunsets in 7 years if the 16th Amendment is not repealed. In short, after 7 years if the American people want to go back to the Income tax after 7 years of the FairTax, it will happen automatically. But if they want to keep the FairTax, then the 16th must be repealed.
The sunset provision of the FairTax code was put in recently to guard against the possibility that the federal government would have both the Income tax and the FairTax to levy on the American people.