(Note, incidentally, that the DHS already has police authority within 100 miles of any border of the US; since that includes coastlines, this area includes over 60% of Americans, and eleven entire states. They also have a standing force of over 45,000 officers, and just received authorization to hire 15,000 more on Wednesday.)
That is to say, the administration is testing the extent to which the DHS (and other executive agencies) can act and ignore orders from the other branches of government. This is as serious as it can possibly get: all of the arguments about whether order X or Y is unconstitutional mean nothing if elements of the government are executing them and the courts are being ignored.
There are 4 qualities of the universe that limit our own intelligence and the intelligence of every other person, collective, organism, machine, alien, or imaginable god. All 200ish of our known biases are attempts to work around these conundrums!