This seems like grandstanding to me if it's really just about the legal justification.
CBP is under the executive branch, so Congress isn't in their report chain. Congress also doesn't decide whether CBP's actions are legal or not; the judicial branch does. I don't find it surprising that CBP doesn't feel the need to justify themselves to Congress.
What I find very odd is that Congress even asked. If you don't want them doing it, pass a law banning it. Why does it matter what USC they're using to justify it?
"Congressional oversight is oversight by the United States Congress over the Executive Branch, including the numerous U.S. federal agencies. Congressional oversight includes the review, monitoring, and supervision of federal agencies, programs, activities, and policy implementation."
CBP is under the executive branch, so Congress isn't in their report chain. Congress also doesn't decide whether CBP's actions are legal or not; the judicial branch does. I don't find it surprising that CBP doesn't feel the need to justify themselves to Congress.
What I find very odd is that Congress even asked. If you don't want them doing it, pass a law banning it. Why does it matter what USC they're using to justify it?