as an example of successful capture of governmental power by private individuals - a city which is basically a fiefdom run by one family and their friends. They had population of something like 50 people, and new people who tried to settle there were actively not welcomed (by the city police). According to wikipedia it looks like some changes were forced upon the city very recently though (if i remember in response to this city scandals CA was mulling 150 people cut-off for incorporation or something like this):

https://en.wikipedia.org/wiki/Vernon,_California#Recent_hist...

"In an effort to modernize the city and stave off the potential threat of disincorporation in the future, for the first time in the city's history Vernon has opened its doors to new residents from the general public."