I've seen Constitutional Free Zone map [1] multiple times, and I've tried to substantiate the claims [2] made by the ACLU (American Civil Liberties Union) [3] but everything I've found so far points back to the ACLU (American Civil Liberties Union); I've yet to find anything that doesn't point back there.
But then I saw this video of DHS (Department of Homeland Security) checkpoint refusals [4] (link via Flutterby [5]), all of which took place inside the United States (and not at the border), one of which was at least 30 miles from the border. So perhaps there is something to that ACLU article.
Another odd thing about that video—most of the agents would not, refused, or tried to talk about the question “am I being detained?” Oh, and the automatic assumption of guilt when one refuser plead the Fifth [6]. I also found it offensive when the officers admonished the refusers for making their job more difficult.
[1] http://www.aclu.org/know-your-rights-constitution-free-zone-map
[4] https://www.youtube.com/watch?v=u4Ku17CqdZg
[5] http://www.flutterby.com/archives/comments/17149.html
[6] http://en.wikipedia.org/wiki/Fifth_Amendment_to_the_United_States_Constitution