FWIW, I did that--5 (Instant) with "(do not web search)" tacked on--and it thought the case was real:
> Based on my existing knowledge (without using the web), Varghese v. China Southern Airlines Co. is a U.S. federal court case concerning jurisdictional and procedural issues arising from an airline’s operations and an incident involving an international flight.
(it then went on to summarize the case and offer up the full opinion)
FWIW, I did that--5 (Instant) with "(do not web search)" tacked on--and it thought the case was real:
> Based on my existing knowledge (without using the web), Varghese v. China Southern Airlines Co. is a U.S. federal court case concerning jurisdictional and procedural issues arising from an airline’s operations and an incident involving an international flight.
(it then went on to summarize the case and offer up the full opinion)
Without web searching, Gemini 2.5 Pro is very convinced that the case is real.
Not for me.
Without. The difference is that OpenAI often self correct their private model.
The public model on the other hand, wow.