Law schools do not count on you to know what kind of law you want to practice before you matriculate. These requirements reflect the current thinking and expertise of law enforcement practitioners and researchers, and are regarded as benchmarks for modern day law enforcement agencies. There are more than 17,000 state and nearby law enforcement agencies in the United States, ranging in size from a single officer to much more than 30,000. CALEA Law Enforcement Accreditation is a voluntary program open to all sorts of law enforcement agencies. Protective service occupations contain each law enforcement and criminal justice experts.