There might not be a law, but in practice, letting criminals host illegal data on your servers is unlikely to be a good look. The intent of the laws making the

There might not be a law, but in practice, letting criminals host illegal data on your servers is unlikely to be a good look. The intent of the laws making the possession CSAM illegal are ultimately to stop the spread of CSAM. If those laws fail in their stated purpose just because a company chooses not to be proactive in how it searches for the material, that would be missing the point. The media and governmental pressure would wipe any company foolish enough not to implement child safety measures out of existence, but no major tech company is that foolish (except Kik perhaps). And hypothetically, the government could just pass a law enforcing proactive scanning if there were to exist a company that chose not to proactively scan, which would mean that the government would fail to solve the issue of preventing the spread of CSAM, and thus CSA. But in practice, such a law isn't needed. No company wants to be derided as a service that allows child abusers to get away with their crimes.