what subject matter does the us supreme court not have the power to decide?
"In this case, the Court had to decide whether an Act of Congress or the Constitution was the supreme law of the land. The Judiciary Act of 1789 gave the Supreme Court original jurisdiction to issue writs of mandamus (legal orders compelling government officials to act in accordance with the law). A suit was brought under this Act, but the Supreme Court noted that the Constitution did not permit the Court to have original jurisdiction in this matter. Since Article VI of the Constitution establishes the Constitution as the Supreme Law of the Land, the Court held that an Act of Congress that is contrary to the Constitution could not stand. In subsequent cases, the Court also established its authority to strike down state laws found to be in violation of the Constitution."
http://www.uscourts.gov/educational-resources/get-informed/supreme-court/about-supreme-court.aspx