There is a strong case that this tax would be a direct tax and therefore would not work under the US Constitution
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Additionally, a wealth tax would almost certainly face a legal challenge from well-funded conservative opponents. And it’s genuinely unclear whether it would ultimately be ruled constitutional. The issue isn’t that Congress can’t enact a wealth tax. It’s that if a wealth tax counts as a “direct” tax, Congress would have to ensure that the amount of money coming from each state was roughly the same on a per-capita basis, as there is a provision of the Constitution that bans direct taxes unless the amount collected is drawn equally from the states based on their populations. Given that wealth is not evenly distributed across the states, that equal distribution would be functionally impossible to ensure.
The fate of a wealth tax, then, would hinge on whether it counts as a direct tax. That’s a tough question to answer, because the Constitution itself doesn’t really define what a direct tax is, beyond the fact that the category includes a poll tax, which is a fixed amount charged for every person. Taxes like tariffs and certain others that can’t be fairly distributed on a per-person basis are generally not considered direct taxes. But how all of this would apply to a wealth tax isn’t entirely clear. The Supreme Court weighed in on this question more than 100 years ago — and not in the wealth tax’s favor. In 1895, the court struck down a federal income tax law because it taxed income generated from property, including land and other kinds of personal property, like stocks and bonds. The decision was controversial, and Congress and the states effectively reversed part of it 20 years later with the passage of the 16th Amendment which allowed Congress to tax income without worrying about how evenly it was distributed. But Congress’s authority to tax wealth wasn’t addressed by the amendment, and the Supreme Court hasn’t really returned to the issue in the past century.
Warren’s defenders argue, however, that the court simply got it wrong back in 1895, and that a modern wealth tax wouldn’t count as a direct tax. But the court’s right-leaning justices might approach the tax with a less favorable eye. And the existence of the old precedent could give the court’s conservative justices a way to dispatch a wealth tax relatively easily, which gives experts like Daniel Hemel pause. “A wealth tax could raise trillions of dollars — or, if it’s struck down by the Supreme Court, it could raise nothing,” said Hemel, a law professor at the University of Chicago. “That’s a really big risk if you care about the redistribution of income and you’re trying to figure out how to get it done.”
Then there are the critics who have argued that even if a wealth tax could survive a legal battle, it would be a nightmare to implement and might not raise as much money as Warren and Sanders have claimed. Yang, in particular, has homed in recently on the practical shortcomings of a wealth tax. In the October debate, he pointed out that many European countries tried wealth taxes of their own but eventually abandoned them, in part because they proved so difficult to administer.