Final answer:
The principal law enforcement agency can be a local police department, state police department, or federal law enforcement agencies like the FBI, ATF, and DHS.
Step-by-step explanation:
The principal law enforcement agency varies depending on the level of government. At the local level, the local police department is the primary law enforcement agency. They have jurisdiction over a specific town or county. At the state level, the state police department has authority to enforce statewide laws. Finally, at the federal level, there are different federal law enforcement agencies like the FBI, ATF, and DHS that handle specific matters within the power of the federal government.