I suppose there are roads around them, but there are permanent ones and mobile ones. The internet has some websites about this:
http://www.google.com/url?q=https://...HRopt6Lwlfytxw
The Border Patrol has nearly absolute power to take your stuff, especially at a border crossing, and detain you while they assess your "suspicious" behavior. Their official website is kind of over the top including statements that undocumented aliens do not care about this country (why would they stay here then?) and showing that they have all the power and you don't:
US Border Patrol Being Detained Note that the sense of that is that if you flee, they will shoot you, so the penalty for attempting to flee is death without any court acting.
Some people refuse to ask the inevitable first question—"Are you an American citizen". Some make videos of the encounter.
What Happens If You Don't Cooperate At Inland Check Points? | Fronteras Desk
But the court cases that I recall from law school said they can stop you 200 miles from the border, though some stuff I've seen says it is 100 miles. The permanent checkpoints are less than 100 miles from the border. They have also stopped buses near Rochester, NY, looking for Mexicans. There seems to be no limit on what they can do including tearing your car and RV apart looking for contraband. When they go into your RV, you are kept away from it, so they may be going through your clothing, personal papers, computer, camera memory, money you have there, your prescriptions, etc. No warrant is required. There are claims that at DUI checkpoints, you don't have to open the window or talk to the cop, or you can have some written statement of your rights and hand it to them through a crack in the window. I don't think that works all the time, maybe none of the time. If the officer has "reasonable suspicion" you are in trouble. To people trained to be suspicious, what is reasonable is almost always decided in their favor.
This may be the town where people can't go anywhere without having to stop at a chexkpoint. The Border Patrol is being sued for haraasment:
Border Patrol sued for harassing at Arivaca checkpoint
I just stay away from the southern border. I'm kind of curious about what Tombstone looks looks like, though I suspect it is a tourist trap, but there's a checkpoint just north of there. The only time we've been stopped at any kind of checkpoint was in Santa Fe when we were trying to get to a movie in time. The cop asked if I'd been drinking—I guess everyone gets that question. If you had a half a beer and say "no", you can be charged with obstructing justice even if you are not impaired. Those are leading questions.
You can tell a cop he or she is wrong, is doing something stupid or represents evil. The 1st Amendment protects our right to tell off the authorities. I have told border cops when we've come from Canada that they should have better things to do besides looking for fruit, but if they are having a bad day, are oversensitive, are trying to prove something to the boss, or whatever, I could have been detained for hours and our vehicles ripped apart. They may be able to seize your vehicle for minor things, maybe even fruit. They can keep all your computers to look for bad things and you may never get them back as they get lost in bureaucracy. I think you have to put your vehicles back together yourself. The border patrol checkpoints do not have quite the power of stations on the border, but they have more power than all the local and state police and even the FBI.
Different people have different ideas about "freedom" and some will sacrifice freedom to feel safe. Some never feel safe. I don't care for the presumption I have done something wrong and can be detained and/or searched without any court process. This wasn't what this thread was about in a narrow sense, but I thought the OP might want to know about checkpoints.
Gene