Same thing was proposed here, I don't know what happened to it but since I can still download research I'm assuming it didn't pass.
But really, if you want to protect your kids from seeing this sort of stuff, yes that's all well and good! Opt-in for this program. But essentially having to go to your ISP or government and say "HEY, GUYS, I WANT TO LOOK AT research OKAY" is not something that you should have to do. What about your right to privacy? When did that one go out the window? They've got it the wrong loving way around. This should be an opt-in not an opt-out.