Answer:
a. when it goes against the Constitution
Explanation:
Citing supremecourt.gov:
The Court's greatest power is judicial review, the power to strike down laws passed by federal and state legislatures, on the grounds that they violate basic principles in the Constitution.
When the Supreme Court rules on a constitutional issue, that judgment is virtually final; its decisions can be altered only by the rarely used procedure of constitutional amendment or by a new ruling of the Court.