Here:
https://www.apple.com/child-safety/pdf/Security_Threat_Model...
Reference: https://edwardsnowden.substack.com/p/all-seeing-i
So the details really don't matter as much as the fact that this creates a huge precedent. And, quoting Snowden again, "There is no fundamental technological limit to how far the precedent Apple is establishing can be pushed, meaning the only restraint is Apple’s all-too-flexible company policy, something governments understand all too well." (emphasis mine)
So I might read through that PDF, I might even understand it, but what it can't dissuade me from is a persuasion that yes, governments can and will take advantage of this turn of events, and no, there is no technological or legal barrier that can keep them from doing so once this is in place.