Final answer:
The Supreme Court's decision to declare a Congressional law as unconstitutional showcases the check and balance mechanism in the US government, through a process called judicial review. This decision invalidates the law, ensuring that no branch of government becomes too powerful.
Step-by-step explanation:
In the presented scenario, the Supreme Court's decision in declaring a law passed by Congress as unconstitutional is significant because it reflects the mechanism of checks and balances in the US governmental system. The Constitution gives the Supreme Court the power to review laws and actions by other branches of government through a process called judicial review. If the Supreme Court declares a law unconstitutional, that decision invalidates the law, making it void and unenforceable. This demonstrates the limiting power of the judiciary over the legislative branch, ensuring no branch possesses absolute authority.
Learn more about Checks and Balances