Maybe you could have hash-based blocklists, and mandate that everyone subscribes to an "illegal" list which governments could freely contribute to. But then yo

Maybe you could have hash-based blocklists, and mandate that everyone subscribes to an "illegal" list which governments could freely contribute to. But then you'd have a new problem: what if someone posts an image of the Tianenmen Square protests? They'll get added to the "illegal" lists despite their value. So maybe you'd also need a few community-maintained "not illegal" lists with some sort of voting system to decide whether to host something...it'd be messy, but it's not an unworkable problem.