At the county level, governments are elected to enforce the law.
The apex agency that ultimately enforces the law at the country level is the government of the country. The government appoints and runs the subordinate agencies that exercise power based on the laws passed by the legislature of the nation.
At different levels of administration, there are different authorities with the right given by the government to enforce laws passed by it. There are various types of laws which includes criminal law, family law, and so on. The laws are separated for each state in the US.
