Answer:
The Supreme Court declares a law passed by Congress "unconstitutional" based on their interpretation of the Constitution.
Explanation:
The "Supreme Court" is considered to be the highest federal court which reviews the different branches whether they are in line with the Constitution. Such review is termed "judicial review." It is also the role of the Supreme Court to check the president's actions as well as the laws that have been passed whether they are constitutional or not.
"Checks and balances" makes sure that the three branches would remain fair when it comes to their power and not one will become greater than the other.