This question is a difficult one to answer as different states give differing powers to private security firms. Both public law enforcement and private security wear uniforms for most jobs and require training before being given that uniform. Authority is different with the public officer usually having more authority to arrest while the private firm has more ability to stop and question someone without the same standard of due cause. More states or cities require some sort of degree whether a four year or two year college degree to really be accepted into a police academy which trains them in the ways the states or cities would want them to act, sort of a practice on the job. Private security usually has their own training facilities if they require training. Most private firms do because of the issues of litigation and the liability which private firms have which differs somewhat from the public sector. The public officers are subject to more training in the truly dangerous jobs they have which risks life and limb every day. Ongoing training is often a requirement for public officers as they work more and more with subjects who are mentally ill and in crisis. Private security does not often work with the mentally ill as their jobs are usually about property and the people who work at that facility. I realize that this answer is not the definitive answer you would want, but the laws are changing and states or cities differ in what is allowed for private security.