Standing
The Article III requirement that a plaintiff have a concrete, personalized stake in the outcome — injury, causation, and redressability.
Beyond the constitutional minimum (injury-in-fact, causation, redressability), justiciability also requires ripeness (the harm is not too speculative), no mootness (a live controversy persists), and that the question is not a political question committed to another branch. These doctrines keep federal courts within the case-or-controversy limit.