That's what the ACLU says, but in practice, USBP only screens interior-bound traffic from the southern and northern land borders. I'm not talking about CBP or ICE or other agencies.

1. That's not "what the ACLU says", it's what the federal government says. https://help.cbp.gov/app/answers/det...-border-patrol

2. What "land border" would a Greyhound bus from Orlando to Miami be coming from? https://www.nbcnews.com/news/latino/...rights-n841141

I'm talking about checkpoints. You're talking about USBP activities. No point to continue here.

I agree, since (a) you never said "checkpoints" anywhere in your discussion, and (b) they're absolutely free (as evidence shows) to "inspect" people regardless of the direction they're going or their proximity to an actual land border.

What is the difference between CBP and USBP?

It’s a bit less than obvious.

CBP has three main law enforcement divisions, but you’re only likely to see to two of them unless you’ve seriously screwed up.

USBP enforces immigration laws at and near the border. Their uniforms are normally green.

CBP Field Operations handles normal entry at airports and designated crossings, issues most non-immigrant visas, etc. Their uniforms are normally blue.

CBP Interdiction has mission overlap with parts of DEA and USCG, blocking drug imports and other smuggling. They wear khaki, but I’ve never run into one of their officers “in the wild.”

There’s also ICE, HSI, and USCIS, but they aren’t part of CBP.

USBP should be noted is one of those three LE divisions.

The reason no one runs into Interdiction (technically, it's CBP Air and Marine) is because they're usually in the air or on the water.

Also, it should be noted that HSI is a division of ICE, not a separate agency. (Although the HSI folks wish they were a separate agency.)