Which amendment was used by the Rehnquist Court to increase states' powers as opposed to those of the federal government?
Disagreement over the deserved power of the federal government as written in the Constitution might still be commonplace if this amendment had not been ratified. After this amendment was passed, if the federal government attempted to "persuade" a state to enforce a federal statute, it was considered unconstitutiona.
The states rights were protected by the 10th Amendment. This Amendment states that anything the federal government doesn't do can be done by the state. For example, the federal government is not in charge setting state income taxes. Because of the 10th Amendment, the federal government cannot take over that responsibility of it wants to; the State sets its own income tax.