Dealing with an intern at work who I suspect is doing exactly this, I discussed this with a colleague. One way seems to be to organize a face to face meeting where you test their problem solving skills without AI use, the other may be to question them about their thought process as you review a PR.
Unfortunately, the use of LLMs has brought about a lot of mistrust in the workplace. Earlier you’d simply assume that a junior making mistakes is simply part of being a junior and can be coached; whereas nowadays said junior may not be willing to take your advice as they see it as sermonizing when an “easy” process to get “acceptable” results exists.
On a positive note: I can remember mentoring some young people and watching them comb through blogs to learn about programming. I am so old that my shelf is/was full of O'Reilly books. By the time I was mentoring them, few people under 25 were reading O'Reilly books. It opened my eyes that how people changes more than what people learn. Example: Someone is trying to learning about access control modifiers for classes/methods in a programming language. Old days: Get the O'Reilly book for that programming language. Lookup access modifiers in the index. 10 year ago: Google for a blog with an intro to the programming language. There will be a tip about what access modifiers can do. Today: Ask ChatGPT. In my (somewhat contrived) example, the how is changing, but not the what.