ChatGPT is not someone. It's a tool.
So is a textbook. Still not OK to copy homework from it.
Textbook has an author that you can copy. You can't copy output of an auto suggest, it's just yours.
It does not matter if author is human or computer.
If there is a spelling bee, but student is secretly using spellcheck on the phone, they are cheating.
If there is a math speed competition, but student is using a calculator on the phone, they are cheating.
If it's a calculus exam, but student is using Wolfram Alpha (or TI-89) to calculate integrals and derivatives, it is cheating.
If it's a written exam but student is using ChatGPT to write the text, it is cheating as well. Not that different from previous cases.