Final answer:
The power to declare acts of Congress or the President invalid is called judicial review, established by the Supreme Court in Marbury v. Madison in 1803 and serves as a check on both legislative and executive powers.
Step-by-step explanation:
The power to declare acts of Congress or the President invalid is known as judicial review. This power was established through the landmark decision of Marbury v. Madison in 1803, where the Supreme Court asserted its authority and assumed the capacity to declare laws unconstitutional.
Judicial review is a critical check on the powers of both the legislative and executive branches of government, ensuring that their actions comply with the Constitution. Although the Supreme Court initially hesitated to use this power frequently, it has become a fundamental aspect of the American system of checks and balances.
Congress, on the other hand, has different mechanisms to limit the President's power, such as refusing to declare war or provide military funding, requiring Senate approval for appointments, and having the ability to impeach the President.