>Uncertain regulations aren't allowed under US law

Uh, I'm fairly sure that's false? What law are you referring to?

As an example of what I'm saying, antitrust regulation is uncertain in the sense that we don't always know when a merger will be blocked or a big company will be broken up by regulators.

It looks like this is for criminal law. Would changes to the tax code for companies which deploy AI be affected by this doctrine? Can you show me a specific example of an overly vague tax code being struck down on the basis of the vagueness doctrine?

Do you think the GDPR would be unenforceable due to the vagueness doctrine if it was copy/pasted into a US context?

BTW, even if a regulation is absolutely precise, it still creates "regulatory uncertainty" in the sense that investors may be reluctant to invest due to the possibility of further regulations.