[durzagott]

So, with Face ID, can you prevent someone trying to compel you to unlock your device by simply closing your eyes or looking away?

[tbassetto]

Yes. If you have time to do it, also press 5 times on the on/off button, it disables Face ID and forces entering the PIN. It's an iOS 11 feature, I just tried on my iPhone 6 and it disabled Touch ID.

[huxley]

That was the way it was described in the Keynote

[have_faith]

How do you know when to open your eyes again?

[fletom]

You can open your eyes but not look at the phone.