Federalism
In the United States Constitution for example, the federal government and state governments both have power. When states and the federal government do not agree on something, the federal government can sue the state in court using the Supremacy Clause in Article VI of the Constitution. This case can go as far as the Supreme Court to decide which side is right. The federal government does not always do this. It has taken no action when several states made marijuana legal or when prostitution was made legal in parts of Nevada. It has sued over an immigration law in Arizona.