In most cases, that's a necessary but not sufficient condition to legally shoot someone.

If ICE is breaking down my door, the legality of using lethal force against them is irrelevant. They don't concern themselves with the law or constitutional protections, so there's no reason for me to. It's not like I can expect access to legal counsel or judicial process if I'm arrested by them. So if it comes to a direct confrontation with ICE, my life and liberty are essentially null and void anyway, and I will therefore respond accordingly. Better to die in a shootout with them than get taken to some black site, outside of any legal jurisdiction, to endure god knows what.