[ ... ]
The law governing the posse comitatus has changed little since its origin in Anglo-Saxon England, around the time of King Alfred the Great in the ninth century. Northwestern University Law School’s Journal of Criminal Law & Criminology is producing a symposium issue on arms law and policy. My contribution is an article on Sheriffs and their posses. (Draft available here.)
[ ... ]
From Anglo-Saxon times until the present, a core power of the Sheriff has been the authority to summon posse comitatus–”the power of the county.” Like jury service, posse service is a mandatory duty of the citizen. When the Sheriff, in his nearly unlimited discretion, summons the posse, the citizen must respond. Traditionally, the group responsible for potentially serving in a posse was approximately the same as those responsible for serving in the militia–although the upper and lower age limits for the posse were wider, and the posse had fewer exemptions (e.g., certain professions) than did the militia.
[ ... ]

Internal link URL's
http://scholarlycommons.law.northwestern.edu/jclc/
http://ssrn.com/abstract=2427430 Free registration required

http://www.washingtonpost.com/news/v...sse-comitatus/