In re David C.

[798] OPINION OF THE COURT Memorandum. The order of the Appellate Division, insofar as it dismissed the appeal by Michael C., should be affirmed, without costs. The Appellate Division did not abuse its discretion in dismissing the appeal to that court for mootness (see, Matter of Anonymous, 55 NY2d 1021). The appeal by David C. should be dismissed, without costs, for mootness. We decline to adopt petitioner’s contention that all retention proceedings — because they are necessarily short-lived and therefore typically evade review — should be subject to review irrespective of mootness. The fundamental principle that a court’s power to declare the law is limited to determining actual controversies in pending cases is subject to an exception that permits the courts to preserve particular issues which are recurring, substantial and novel, and typically evade review (see, Matter of Hearst Corp. v Clyne, 50 NY2d 707, 713-715). Even if we were to accept petitioner’s contention that retention orders typically evade review, no blanket rule could be made for retention proceedings. The determination whether to consider particular issues despite their mootness must depend additionally on the recurring, novel and substantial nature of those issues as they are presented. Here, we are persuaded that the issue raised — whether an involuntarily retained patient who has not requested a hearing may nonetheless obtain a "rehearing” of a retention order pursuant to Mental Hygiene Law § 15.35 — is not sufficiently substantial or novel to warrant an exercise of this court’s exceptional discretion to retain the appeal despite mootness (see, Matter of Barbara C., 64 NY2d 866, 868; Matter of Hearst Corp. v Clyne, 50 NY2d 707, 715, supra). Chief Judge Wachtler and Judges Simons, Kaye, Alexander, Titone, Hancock, Jr., and Bellacosa concur. Order insofar as it dismissed the appeal by petitioner Michael C. affirmed, without costs, and appeal by petitioner David C. dismissed, without costs, in a memorandum.