Hi there!
The principle of federalism is a major feature of the U.S. government and one the framers had in mind at the Constitutional Convention. In the U.S., federalism operates by ensuring the states have their own power and rights but still making them second to the national government on most issues. It also grants the rights of states to interpret and refuse to follow the acts of national branches should the actions be unconstitutional. This does not however make the states the supreme interpreter of the Constitution. Rather, they have equal power in interpreting it just as the other branches of government do. The Constitution promotes federalism by granting the states rights not guaranteed to the national government nor prohibited by the states to the states and people respectively. It also leaves it to the states to enforce local laws and law enforcement in it's own jurisdiction.
