The government's plan? No idea, because they still don't have any idea. It might involve requiring you to install software to use any social media legally*. Or it might not require new software, but require you to upload your photo ID or a selfie (on the promise that they will totally delete the photo as soon as they're finished verifying it, pinky swear!). The law was passed 6 months ago in a rush, and is now 6 months away from coming into effect, but we still don't know. Because the government did not do its due diligence in planning this out. It didn't even have sufficient time for proper public submissions.

If you meant my idea? I didn't specify. It could be designed either way. To assume anyone who hasn't specified an age is an adult and allow them through, or to block by default in order to ensure age verification is being proactively provided. Personally, I would advocate for the former, but even the latter would be vastly superior to any other system I can think of.

Importantly: it wouldn't be any software you have to install. It'd be a basic feature of the operating system. Like your operating system probably already has child controls on it; you just don't use them. (Windows, macOS, iOS, Android, and at least Ubuntu Linux all certainly do, to different extents.) In the stricter scenario where it blocks if no age is provided, you would have to set your age up through your operating system's settings. The key is: it relies entirely on trust. You can enter whatever age you like; there's no checking of your face or your documents, so there's no possibility of privacy invasion. This provides compliance with the intent of the law for children by requiring parents to enter the correct age for their kids and set sufficient locks on it to prevent the kid easily bypassing it.

* including any Lemmy, Piefed, or Mastodon servers, unless they can receive a specific exemption—and whether fediverse owners try to receive such an exemption and operate legally without age verification, or they implement the system, or they simply try to fly under the radar and hope they don't get in trouble, is going to be a point that all fediverse admins where either the admin or the server are based in Australia are going to have to consider once the law comes into effect.