They sell data derived from the data. But it's not, like, a hash function - you can absolutely deduce the source data from it. In fact, that's the entire purpose. You use the aggregation and whatnot bullshit to find individuals, track them, gain insight into their living situation and patterns, and acquire evidence of crimes. Typically that requires a search warrant.
If you couldn't go backwards Palantir wouldn't have a market. So, I would consider that a loophole.
> They sell data derived from the data.
Do they? I don't think they even do this, either.
I have really strong knowledge of this from ~10 years ago and weak knowledge from more recently. I'm happy to be proven wrong but my understanding is that they don't sell any data at all, but rather just consulting services for processing data someone already has.
One of those consulting services is probably recommending vendors to supply more data, but as far as I know Palantir literally do not have a first-party data warehouse at all.