It is part of a layered approach to border enforcement. These checkpoints are not typically 50-100 miles from the border, but sit on chokepoints of travel moving away from the border. You folks up here don't see it but this area is much more urbanized, but down south there can be 40 miles of road leading from a POE before it intersects an east/west route then another 40 miles or more before it reaches another north/south road. Take a look at a map, Interstate 19 coming out of Nogales, SR 286 coming our of Sasabe. SR 85 I believe, coming out of Lukeville.
No, my knowledge of the law is quite fine, yours is questionable. The Constitution is not absolute, despite your attempts to show otherwise. The Second Amendment is not absolute, nor the 4th or 5th. I think the only one that might be would be the 13th, slavery.I suggest you read these BB, as your knowledge of the Law is lacking.
So far as your right to take pictures of me doing my job, I have said before, I could care less. I will blind your camera with my 800 lumen flashlight if I like, that is my right I suppose. And if you are in an area I have responsibility over, I will challenge you on your reason to be there. Just because you have a right, doesn't mean you should.
b.b.