Article III of the Constitution limits federal courts to deciding actual cases and controversies. To sue, a plaintiff must prove three elements: an injury in fact (concrete and particularized), a causal connection between the injury and the defendant's conduct, and a likelihood that a favorable court decision will redress the injury. The Supreme Court has tightened standing requirements in recent years, most notably in FDA v. Alliance for Hippocratic Medicine (2024), where the Court held that organizations that voluntarily incur costs to advocate for clients don't automatically meet the injury requirement.