Defined: A legal phrase for what we all know Judges do: look a law, a policy, an act, a piece of legislation, etc., and assess whether it is or is not constitutional. This seems like such a deeply established concept that it’s hard to imagine that nowhere in the constitution does it say that judges have this power!
So where does this idea come from?
This comes from the landmark 1803 decision, Marbury v. Madison. In 1789, Congress passed the Judiciary Act, which in part, allows a person to bring their case straight to the Supreme Court of the United States (generally not allowed with few exceptions) if you were seeking a “writ of mandamus” (which is basically when you’re asking a higher court to tell a lower court to perform their duties).
Marbury uses the Judiciary Act to bring his writ of mandamus to the Supreme Court. The Supreme Court says that actually, the Judiciary Act is unconstitutional. The court says that the constitution already explicitly mentions the circumstances in which a person could bring their case straight to the Supreme Court and Congress can’t just add another method.
Marbury says hold on, Court: who says that you’re allowed to say whether this act is unconstitutional? The court said while it hasn’t been explicitly said before, #1 we’ve been saying things are and are not unconstitutional for a long time now so it would be silly to stop now, and #2 there are many provisions in the constitution (i.e. The Vesting Clause, Arising Under Clause, Supremacy Clause, Oath Clause) that lead us to believe strongly that that’s our job.
So while we all know that this is what courts do, it was in fact made the law more than 200 years ago. This may seem uneventful now given how settled this idea is, but it’s important to note that this remains the single most important decision in American constitutional law and at the time was considered an “epic” and “genius” decision.