Criminal Justice encompasses all types of law enforcement - park police, university police, airport police, etc.; as well as detention - jails, prisons, immigration detaining centers,; probation and parole. There are also "civilian" jobs in fields such as evidence technicians, dispatchers, inmate processing. The degree is "transferable" to other fields, especially social services - as you will acquire an ability to learn and apply law, and an understanding of different types of people and how to best interact with them.
Some people with CJ degrees become paralegals, but this usually requires a paralegal certification, or a strong networking connection who is willing to give you that opportunity. The paralegal field is very competitive, but could be worth pursuing if you are considering law school. The starting pay is usually not very high, but there is room for growth and experienced paralegals can be paid quite well.