Given your hope, shouldn't you be asking software licensing questions to every candidate? Irrespective of them mentioning ChatGPT? Otherwise, what happens if two months in they start using ChatGPT?
ChatGPT isn't the only legally risky software licensing issue.
A lot of people, including me, will use a search engine to find a solution to a given problem. That solution may be covered by copyright, and subject to a license which is not compatible with the company's business model. Some companies prohibit the use of GPL software. I consulted for one company which required authorization before using any open source software.
So it seems to me you should already be asking people about these sorts of issues.
