[sobellian]

There is a line between tax and unlawful taking. The constitution forbids taking of property without due process or compensation. No, the government can't just take whatever it likes from anyone and call it a tax.

Taxes generally demand payment in the form of general assets, but taking targets specific identified property. Likewise taxes are raised from a general category whereas taking singles out one or a few properties. Now if it was just the targeting of AI companies you could argue it's a one-time AI tax rather than singling out those companies for taking. But once you state that the tax must be paid by shares (and not just assets equal to 50% of market cap) that looks less like a tax and more like appropriation of equity for public good without compensation.

There are other vulnerabilities too - income taxes are explicitly exempted from apportionment. This "tax" would probably run afoul of apportionment.

[thedevilslawyer]

Eminent domain. It can be made to apply to AI.