I live in Michigan and the state grants private police, "misdemeanor arrest authority while on active duty, on their employer's premises and in full uniform." http://www.michigan.gov/mcoles/0,1607,7-229-41626_42413---,0...

Edit/ I should mention, in my post, that there is some licensing required to become a private police force /Edit

I worked at a biopharma that had a private police force.