You can't refuse to be scanned by ICE's facial recognition app, DHS document say

I am not a lawyer.

There may be some confusion here. It's legal for anyone to take a photo of anyone else in public, with few exceptions. TFA is not saying that ICE is forcing people to stand for a photo, it's saying that once ICE takes a photo, they can do stuff with it.

As an aside, it's my understanding that, unless someone is arrested, they're free to wear whatever clothing they like including something that covers their face. Probable cause is required for arrest, therefore ICE cannot force you to uncover your face. I'm not sure this has been tested much though, especially with folks temporarily detained.

Second aside, I anticipate a ton of lawsuits where folks give clear and convincing evidence of US citizenship and are unlawfully detained thereafter.

Yet false arrests without probable cause are happening. The limits on this are being tested on real people. For some voters, those are the right people to test it on.