No, a court did not declare that. The case involved a person trying to register a work with only the AI system listed as author. The Supreme Court decided that you can't do that, you need to list a human being as author to register a work with the Copyright Office. This stems from existing precedent where someone tried to register a photograph with the monkey photographer listed as author.

I don't believe the idea that humans can or can't claim copyright over AI-authored works has been tested. The Copyright Office says your prompt doesn't count and you need some human-authored element in the final work. We'll have to see.