We address first the principles of standing relevant to the claims asserted by the several categories of petitioners in this case. In essence the question of standing is whether the litigant is entitled to have the court decide the merits of the dispute or of particular issues. This inquiry involves both constitutional limitations on federal-court jurisdiction and prudential limitations on its exercise. . . .In both dimensions it is founded in concern about the proper—and properly limited—role of the courts in a democratic society. . . .
In its constitutional dimension, standing imports justiciability: whether the plaintiff has made out a ‘case or controversy’ between himself and the defendant within the meaning of Art. III. This is the threshold question in every federal case, determining the power of the court to entertain the suit. As an aspect of justiciability, the standing question is whether the plaintiff has ‘alleged such a personal stake in the outcome of the controversy’ as to warrant his invocation of federal-court jurisdiction and to justify exercise of the court’s remedial powers on his behalf. . . . The Art. III judicial power exists only to redress or otherwise to protect against injury to the complaining party, even though the court’s judgment may benefit others collaterally. A federal court’s jurisdiction therefore can be invoked only when the plaintiff himself has suffered ‘some threatened or actual injury resulting from the putatively illegal action . . . .’[FN10] . . .
FN10. The standing question thus bears close affinity to questions of ripeness—whether the harm asserted has matured sufficiently to warrant judicial intervention—and of mootness-whether the occasion for judicial intervention persists. . . .