Client wants full copyright to ChatGPT outputs I generated - do they have a case?

ok so i need some help understanding this situation. I'm a freelance copywriter and I was hired to write marketing copy for a startup - landing pages, email sequences, social media posts etc. Standard project, $4,500 total.

I used ChatGPT to help draft some of the initial copy, then rewrote and edited everything myself. Probably 60% my writing, 40% AI-assisted. Never hid this - lots of writers use AI tools now.

Client found out (I think someone told them?) and now theyre demanding I sign over "full copyright" to all the content AND threatening to withhold final payment. Their argument is that since AI generated part of it, there's no copyright to begin with, so I "misrepresented" the work.

My contract just says I deliver "original marketing copy" and they get usage rights. Nothing about AI tools or work-for-hire. Do they have a legal leg to stand on here??

Freelance copywriter here. I dealt with a client dispute over AI-assisted content last summer. The client hired me to write 20 blog posts at $500 each. I used ChatGPT as a brainstorming and outlining tool, then wrote the actual content myself with substantial editing and original research. The client found out I used AI in my process and demanded a full refund.

My contract did not have any language about AI tool usage, which was the root of the problem. The client argued that using AI constituted fraud because they thought they were paying for purely human work. I argued that every writer uses tools and that AI was just another tool in the process.

I consulted with a contract attorney who advised me that without explicit terms prohibiting AI usage, the client had a weak claim. The deliverables met all specifications for quality, length, SEO requirements, and deadlines. The method of creation was not specified in the contract, so there was no breach.

We reached a compromise: I kept the full payment but agreed to disclose AI usage going forward. Since then, I have updated all my freelance contracts to include an explicit clause about AI tool usage, specifying that I may use AI tools for research, outlining, and initial drafting, with all final content being substantially written and edited by me. I recommend every freelancer do the same 🤷.