Sanitariums? Do they still have those?
Tombstone, as far as I know. If you check out their FAQs on the website, I think you'll find that what these guys did was out of step with the project's intentions:
No "hostile" confrontation with intruders will be allowed. The MMProject participants will only "spot and report", the USBP takes it from there.
We will seal the border by our presence, but will not violate anyone's civil rights, and will not abuse anyone from any country.
http://www.minutemanproject.com/FAQ.html