The plaintiffs’ arguments in Moore v. United States have little basis in law — unless you think that a list of long-ago-discarded laissez-faire decisions from the early 20th century remain good law. And a decision favoring these plaintiffs could blow a huge hole in the federal budget. While no Warren-style wealth tax is on the books, the Moore plaintiffs do challenge an existing tax that is expected to raise $340 billion over the course of a decade.
But Republicans also hold six seats on the nation’s highest Court, so there is some risk that a majority of the justices will accept the plaintiffs’ dubious legal arguments. And if they do so, they could do considerable damage to the government’s ability to fund itself.
The Sixteenth Amendment exists not because of the limitations imposed by Pollock v. Farmers, but because Congress was concerned that the Supreme Court might strike down further income tax laws even though they were within the powers conferred by Article 1. Congress thought the Supreme Court had gone too far (and they likely did) and wasn’t sure how far they would go so they took it out of the Supreme Court’s hands.