I haven't followed this story that closely, so forgive my ignorance. But did they arrest these people, or simply detain them to clear them out of the area of the temple for their own safety?

I'd say that the former is blatantly unconstitutional, while the latter is a permissible function of the state's police power. It's akin to clearing out a night club after there's been a shooting. It's got to be done to ensure public safety and the efficient investigation of a crime. But anything more than taking down names for witnesses, and clearing people out of the area, is an abuse of police power.

It's cool. Back when I lived in Utah, I met quite a few polygamists including members of the Owen Allred and Tom Green families. Since practically everyone in Utah is related in some way or another, I was close friends with a non-FLDS second cousin to Ervil LeBaron. My friend's LDS parents grew up in the Colonias along with their FLDS relations who had been "fostered out" after the Short Creek raids. Hanging out with this man's family gave me an opportunity to learn about an often secretive yet growing subculture.

To put it mildly, his Hildale relatives would not have approved of our friendship. Polygamist groups vary in their use of violence towards perceived apostates and cultural outsiders. Some polygamous groups avoid conflict with external authorities; other groups advocate and commit multiple murders, in addition to other state and federal crimes. Prior to his capture, Warren Jeffs was on the FBI's Top Ten Fugitive List and was considered "armed and dangerous". Here's the link:

http://www.fbi.gov/wanted/fugitives/cac/jeffs_ws.htm