Federalism is never actually mentioned in the Constitution. However, there are various clauses that spell out the idea that there are some powers that are given to the federal government. This implies that the other powers are given to the states. The main place in which this can be seen is in Article I, Section 8. There, the Constitution lists a number of powers that are given to Congress. Outside of the original Constitution, the main place where federalism is seen is in the 10th Amendment. This amendment says that any rights that are not given to the federal government (and are not taken away from the states) are reserved to the states. This clearly implies that the states have separate rights that cannot be taken away from them by the federal government.