[Timber Rattler]

A DEA agent boarded the train at the Albuquerque Amtrak station and began asking various passengers ... where they were going and why.

That's none of your damned business, G-Man!

[varyouga]

Didn’t you hear? Refusing a search is now considered probable cause for a search

But it defacto has always been that way...

[tbw2]

The Institute for Justice is fighting this across the board. There were police in Texas targeting cars from out of state for search, in one case threatening a couple with kids to be arrested on suspicion of carrying drug money (to explain the cash they had) and calling Child Protective Services to take the kids.
Of course the parents gave up the money to keep the kids.

And the police intentionally sought out of state drivers because those people were much less likely to have the resources to come back to challenge a court hearing.