I was reading the wiki article about the Pinkerton detective agency, and it mentioned that there was a federal law stating that "[an] individual employed by the Pinkerton Detective Agency, or similar organization, may not be employed by the Government of the United States or the government of the District of Columbia."
Was there an event that led to the passage of the law? Did it have to do with their use in labor disputes? Or was there a rising sentiment against the government contracting private security?
I cannot answer your question, but in their answers to I want to know more about the Pinkerton detectives. Were there many private security agencies like them when they were prominent? What could and couldn’t they do legally, and what’s changed since then? What caused them to fall out of the spotlight, considering they company still exists? /u/kingconani and /u/DHLawrence talk about this very topic.
They go over the brief history of the company, what kind of work Pinkerton Detective Agency performed and how the industry changed toward the end of the 19th century.