Correctional officers are the police in prison and jail. It is their job to enforce all the rules and ensure that arrested or imprisoned people are safe and orderly. These officers are also present in courthouses or anywhere else inmates may be.
While education beyond a high school diploma may not be a requirement, you will need to be trained and pass whatever exams are needed in the state or country in which you want to work. Ensure those qualifications are clearly listed on your resume.