Asking candidates: "Don't use AI" is like all those other arbitrary handicaps that interviewers used to (and sometimes still do) weirdly insist on:

"Write this code, but don't read the API definition (like a normal developer would do in the course of their work)"

"Whiteboard this CRUD app, but don't verify you did it right using online sources (like a normal developer would do in the course of their work)"

"Type this function out in a text document so that you don't have the benefit of Intellisense (like a normal developer would have in the course of their work)"

"Design this algorithm, but don't pull up the research paper that describes it (like a normal developer would do in the course of their work)"

You're testing a developer under constraints that nobody actually has to actually work under. It's like asking a prospective carpenter to build you a doghouse without using a tape measure.