I’m not sure to what degree that this restriction is practically possible with the way the internet works though. You can probably make it work on big websites dedicated to that content, sure (there’s admittedly still the issue of using VPNs to appear to be from a location without such rules, but given that these kinds of laws seem to be slowly becoming more common, maybe that won’t be an issue forever), but children are curious about things kept off limits, and includes teenagers who may seek that content actively. As such, if there’s a reasonably easy way to find that content, they’ll find it, so simply gating big websites isn’t enough. In theory, laws about the matter probably apply to more than just those sites, but consider: small websites based in other countries might just not care about foreign laws, any web service that allows user generated content (which is a lot of them) can potentially be used to share pornographic content, and some such web services are set up in a way that moderation sufficient to actually stop this is not realistic (say, discord servers secretly set up for sharing it, or fediverse instances too small to be notified by regulators, or based in another country, or with inactive moderation that doesn’t notice what is being shared). As such, I don’t think it’s really realistic, short of a type of authoritarian control on any site that allows any kind of user uploaded content that would cause way more harm than what it tries to solve, to actually be able to stop minors from being able to access porn if they really want to. As such, I’d think that a better way of addressing concerns like them getting the wrong ideas about how sex works, or having unrealistic standards of appearance or such, is better sex-ed. When they grow up they’ll be able to access this stuff anyway, so if one is worried about it giving incorrect ideas, it makes more sense to tell them that they’re incorrect, and why, and what the reality of the matter is, rather than try a futile attempt to childproof the internet.