You and I are ethically justified in using deadly force against agents of The State just about anytime we encounter them in their "official capacity". Cops, TSA, IRS, AFT, whatever.
When one of these "people" attempts to enforce some counterfeit "law"- any "law" that is an attempt to regulate or control anything other than aggression or theft- against anyone, they become the bad guy and it is your absolute human right to resist them however you see fit, including killing them if they don't cooperate. It is "illegal", and therefore suicidal, of course, but it is still your right. I will never condemn anyone for killing an agent of The State under such a circumstance. I can't even get too worked up over an actual thief/aggressor killing an enforcer. A bad guy killing another bad guy doesn't concern me too much, and it's one less enforcer you and I have to deal with.
Any "traffic stop"; any airport scan or pat-down; any demand to see your permit or license; any official interaction at all is a credible threat to initiate force against you. You're foolish if you don't recognize the danger. You twitch an eyelid at the wrong moment and the agent of The State will kill you in the name of "officer safety". That constitutes a credible threat to your life, liberty, and pursuit of happiness. Do you disagree?
Many people don't want to hear this truth. They would rather weasel-word their way around the foundational facts of the matter. They don't want to be seen as "extreme". Those who defend themselves against bad guys are not "extreme"; those who support the bad guys and pretend their actions are legitimate in any way are the ones who are extreme.
No, I am not going to resort to deadly force against an agent of The State unless I feel I have nothing to lose. And, yet, the parasitic vermin of The State seem to be working really hard to make sure that those who love and really understand liberty are backed into a corner, with nothing to lose, as soon as possible. You'd think they are just dying to start a war over liberty. Well... It's their funeral.