Are you a fan of Hollywood cop films? If you are, you may know that a common plot line in these movies is jurisdiction friction, or when some kind of tension between local police (usually the hero) and federal investigators (usually the antagonist) takes place over who has control of an investigation. Take, for example, the film Rush Hour. In this movie, an LAPD police officer (Chris Tucker) tries to help a fellow Chinese cop (Jackie Chan) find the abducted daughter of the Chinese Ambassador to America. While they face many road blocks, one of the biggest obstacles in their investigation is the FBI, which orders Tucker and Chan to stop their investigation because it is outside of local jurisdiction and a matter of federal jurisdiction.
What this common Hollywood plot line reveals is the nature of a federal government. A federal government is a system of dividing up power between a central national government and local state governments that are connected to one another by the national government. Some areas of public life are under the control of the national government, and some areas are under control of the local governments. For this reason, cop films like to create drama by making the federal government and local government bump heads over who should be investigating the crime at hand. Federal government systems usually have a constitution that specifies what areas of public life the national government will take control over and what areas of public life the state governments will take control over.
