The United States Supreme Court has to help determine the rules of the constitution since they are very vague and many times complex. Since the states rights in the constitution are vague or doesn't even mention many of them, the Supreme Court must rule on these matters. The Supreme Court must rule on the scope and limits of both the federal and state laws and/or authority.
The Supreme Court is the highest court in the U.S and they can actually overturn any action by the government as unconstitutional if they find it to be so. In addition to state and federal laws, the Supreme Court can rule on local laws if the case makes it to the court.
