They don’t block CSAM because “it’s illegal” - in fact, they can’t be forced to do it without it breaking your 4th amendment rights. Instead, all CSAM reporting and blocking is done at-will by these companies, and some don’t participate (Apple[0]), so it’s a policy decision by these companies.

I imagine unblocking someone due to them being exonerated by a government entity is legally risky - perhaps doing so would be considered enough proof/evidence to deem the entire CSAM scanning practice as a search/seizure at the request of the government.

0: https://www.hackerfactor.com/blog/index.php?/archives/929-On... • “ According to NCMEC, I submitted 608 reports to NCMEC in 2019, and 523 reports in 2020. In those same years, Apple submitted 205 and 265 reports (respectively). It isn't that Apple doesn't receive more picture than my service, or that they don't have more CP than I receive. Rather, it's that they don't seem to notice and therefore, don't report.”

It’s unwise to depend on Google with decades of history of poor customer service.

To be fair, users of many internet services exposed themselves. The warnings about that were loud and clear. I don't know if using their free service counts as a formal business relationship, that might make recourse more difficult. I think the service provider has the right to close any and all relationships unilaterally.

Cloud storage for anything valuable.

Note that it was the telehealth provider who provided the images to Google in the first place, not the SF techie dad.