Identify devices, not people.

Distinguishing between child-locked and unlocked devices is something any website should be able to do easily. Adult-only should be a config setting.

Vendors shouldn't sell unlocked devices to kids.

Then it's up to parents take sure their kids only have locked devices. (Or not, if they're okay with it.)

And there obviously gonna be market for "verified" devices. Not like there is anything at all that could stop people of any ages looking at porn.

Sounds like a problem. Luckily it turns out my phone has two cameras and a laser dot projector pointed at my face right now. Not hard to imagine a future solution to this issue were we to pass this legislation, sadly…