Congress recently voted on a law that would allow the implementation of harsher sentences for people working in the NSA who disclose confidential information. The president vetoed the bill, but was eventually overruled by a 2/3 majority of Congress. In the end, the Supreme Court declared the bill unconstitutional. The actions taken by the Supreme Court are an example of

checks and balances

Explanation:

There are three distinct branches of the government and each have its own distinct purpose and functions. Even though the President of America has supreme powers in the country he does not enjoy ultimate power.

Even though the President of America voted for the bill that allowed of harsher sentences for the people working in the National Security Agency who discloses the confidential information to others, the Congress overruled the bill by a 2/3 majority.

Finally the bill was declared unconstitutional by the Supreme Court. Thus it is the function of the Supreme court to guard the constitution and the right of its citizens. The Supreme court checks and balances the rights provide to the citizens.

Thus the answer is checks and balances.