"You have traveled across a state line; show me your papers."
Please, let’s not overreact at every turn.
Yes, I can think of plenty of scenarios in which LE/HS agents would be required to check passengers upon deboarding a train or an airplane, for that matter. Do people really think that the security is only concerned about what happens when the conveyance is underway?
If HS got information that someone may have brought a dirty bomb on a train, would it be okay for them to check for it or would that be “an amazing abuse of police power”?
If HS had information that a geiger counter held by an onboard air/train marshall went off, would it be okay to check passengers as they deboarded?
Let’s get a little real here.
Just sayin.