Which power is considered the most significant power of the judicial branch?

Judicial review is considered the most significant power of the judicial branch because it allows the courts to interpret the Constitution and to invalidate laws or executive actions that are found to conflict with constitutional provisions. This power was established in the landmark case of Marbury v. Madison in 1803, which asserted the judiciary's role in ensuring that the legislative and executive branches operate within the boundaries set by the Constitution.

By exercising judicial review, the courts uphold the rule of law and protect individual rights against potential overreach by the other branches of government. This mechanism serves as a critical check and balance, ensuring that no law can stand if it is deemed unconstitutional. Consequently, judicial review plays a fundamental role in maintaining the integrity of the legal system and reinforcing the principles of democracy and governance in the United States.