Well, no LEO's except OBG have chimed in, so I'll add one more thing. Actually, it's not clear what you're asking for, Martin. I mean, the bit of California's state law does outline what circumstances a posse comitatus could be called out, at least in California. Is that not what you're after?

The only example I have been able to find so far of a modern use of the posse comitatus (multiple civilians) happened in 1977 in Aspen, Colorado. Ted Bundy escaped from the jail and local civilians were called out, armed with their own weapons, to hunt him down.

I did run across this fascinating bit of posse comitatus trivia. Francis Scott Key probably would never have written the Star Spangled Banner if it weren't for a Maryland posse comitatus formed to capture some British soldiers causing mayhem in the county. Without the posse, Francis Scott Key would never have been on the ship watching the British attack Ft. McHenry, and would not have been so moved and inspired to see the American flag still flying proudly come morning that he then composed the Star Spangled Banner. You can read more about this story here .