An age limit on alcohol
This has a very clear means of enforcement, since you can require age checks at the point of purchase and revoke licenses if someone violates that.
This law is a lot harder to enforce, because what exactly is "social media"? If the kids are all blocked from Facebook and whatnot, they could rally around the comments section of a local newspaper or something (or even something like Lemmy, which isn't large enough to properly regulate). Kids are creative, and a lot of parents (at least here) are pretty oblivious to what they actually do on their devices.
So I'm skeptical of this law, but we'll see how it plays out.