> But then HN would still riot, because you would need to require all apps to be approved by a central authority (no unauthorized browsers) OR you need to lock down browser engines to those that respect the list somehow (maybe by killing JIT, limiting network connections).

I don't think you need to do that. You can pass a law without creating a technical mechanism that automatically enforces the law. The law doesn't even need to be perfect.

So what if you can still patch a browser yourself. Kids can steal cigarettes but laws against selling cigarettes to kids are still broadly effective.

So what if its technically possible for a vendor to ship a violating browser. Go after violaters with the legal system, not with the OS.

So what if there's a foreign vendor with a violating browser out of the reach of the law. You'd still have made the ecosystem vastly better even if there's gaps and loopholes.