It's been established many times that it is perfectly legal in US law to film US police on US soil .. there's been state by state settings of acceptable distances, etc.
ICE / DHS / Border patrol aren't US police, of course - they are immigration enforcement agents with more limited powers despite assertions by the current US federal administration to the contrary.
The video gives vague platitudes about filming limits just saying "do not obstruct" well duh, now define what not obstructing means, show case laws about the right radius or whatever else to film. No where does the video show he was "legally obstructing" the policework, just cites that a filmer must not obstruct.
If they even let the investigation happen properly. This is trumpian "investigation" after all.
It doesn't seem to be legal to interfere with police work https://youtu.be/QePoawDA_48?si=0mr-lMR_lIRoBDA_, e.g, film or whistle during an operation. The constitution doesn't apply as naively as you think.