No more illegal than when you say: "Stop! Don't take my belongings out of my sight!"

Since the screeners have no authority of detention, if more than 3-4 people continue walking (hearing impaired, non-English-speakers, earphone-distracted), they can't possibly call enough LEOs to stop them all.

I'd just keep walking. No requirement for the public to participate in THEIR training exercise if you're past the checkpoint, and you've been cleared to the sterile side, so there's no possible justification to call a terminal dump. I see no downside to ignoring them.

Besides, you also could be hustling off the nearest bathroom. They REALLY can't slow you down on such a critical mission. Just say: "No. Gotta pee!"

Now if an LEO says "freeze!", that would be an order I'd take under more serious advisement.