An important note that nobody seems to be reporting on: this is only possible because Apple and Google have control over which apps are permitted on your device.

The US government has no legal authority to ban publishing (including apps) in the US. They do, however, have the ability to regulate trade between the operators of the App Store (Apple) and the Play Store (Google), and app publishers, which is what they're doing here.

Ban the business relationship, and they've effectively banned the publishing. It's an end run around the US constitution, and everyone should be up in arms about it: not just at the US government, but also at Apple and Google for creating a legal chokepoint for mass censorship by the US federal government.

This would not be possible if end users actually exercised control over their own devices. This is how the web works, and it's how everything else on your device should work, too.