A second objection is that the wealth tax proposal is functionally a bill of attainder, which is also forbidden under Article 1 Section 9, and denied to the states under Section 10. The ban was based on the abuse of this process by British governments seeking to punish political dissent. Hence bills of attainder, according to Chief Justice Earl Warren in the 1965 case United States v. Brown, were intended by the Framers to bar “legislative punishment, of any form or severity, of specifically designated persons or group.”
Under the test laid out in the 1946 case United States v. Lovett, bills of attainder identify specific groups (in this case “billionaires”) and impose punishment (taking wealth) without a trial. Laws denying employment to members of subversive organizations have been overturned by this standard; replace “communists” with “the wealthy” and you can see how the class warfare script has flipped.