concurring:
I concur in Judge Newman's thorough opinion, but write separately to emphasize what I view as the narrow scope of the issue presented on this appeal and to add a reason for rejecting the appeal.
Though both the majority and dissenting opinions discuss a witness’s standing to challenge the court’s subject matter jurisdiction of the litigation, the question of subject matter jurisdiction may have many ingredients; this appeal involves only the ingredient of the plaintiffs’ standing to bring the litigation. While certain other ingredients of subject matter jurisdiction, such as the existence of a federal question or the grant by Congress to the federal courts of the power to adjudicate a particular question, may be determined principally by legal analysis, the question of a plaintiff’s standing to sue often turns on his ability to make showings that are largely factual, see, e.g., Gladstone, Realtors v. Village of Bellwood, 441 U.S. 91, 109-15 & nn. 29, 31, 99 S.Ct. 1601, 1612-15 & nn. 29, 31, 60 L.Ed.2d 66 (1979); Duke Power Co. v. Carolina Environmental Study Group, Inc., 438 U.S. 59, 74-77, 98 S.Ct. 2620, 2630-32, 57 L.Ed.2d 595 (1978); United States v. Students Challenging Regulatory Agency Procedures (SCRAP), 412 U.S. 669, 688-90 & n. 15, 93 S.Ct. 2405, 2416-17 & n. 15, 37 L.Ed.2d 254 (1973). For example, he must demonstrate that there is actual or threatened injury, that such injury is fairly traceable to defendant’s illegal conduct, and that there is a substantial likelihood that such injury will be redressed by the relief requested. See, e.g., Allen v. Wright, 468 U.S. 737, 751, 104 S.Ct. 3315, 3324, 82 L.Ed.2d 556 (1984). To make such largely factual showings, a plaintiff may well need, as in this case, to obtain discovery from a nonparty witness.
We all agree that the court has jurisdiction, or power, to determine whether or not it has subject matter jurisdiction. One purpose of recognizing this power is to permit informed, reliable decisions on the jurisdictional issue of the plaintiff’s standing. Where the needed showing as to standing is largely factual, the court must have the power to permit the plaintiffs to conduct a reasonable amount of discovery, if necessary, to prove to the court that they do have standing. Where there is at least a colorable basis for standing, it would be unsound to allow the witnesses to abort discovery relating to standing by arguing that the plaintiffs have no actual standing.
Thus, to the extent that the discovery sought in the present case seeks information pertinent to the issue of plaintiffs’ standing, this relevance provides a reason in addition to those discussed in the majori*167ty opinion for affirmance of the decision of the district court.