OPINION OF THE COURT
Smith, J.Article 10 of the Mental Hygiene Law, enacted in 2007, provides that certain imprisoned sex offenders may be transferred to mental hospitals, rather than being released, when their prison terms expire. The statute raises important questions concerning the procedural and substantive rights of the prisoners to whom it applies, but those questions are not before us in this case. We have here the narrower issue of whether the statute applies to a particular class of prisoners: those who were incarcerated for violating the conditions of a term of postrelease supervision (PRS) that was improperly added to their sentences by the Department of Correctional Services (DOCS) without court authorization. We hold that these prisoners are within the coverage of the statute, which we read as applying to offenders actually imprisoned, even if the procedure that led to their imprisonment was flawed.
I
Both of these cases involve men convicted of serious sex crimes—assaults of vulnerable strangers on the street. Joseph II. assaulted a child, Humberto G. a developmentally disabled adult. Both were sentenced to imprisonment. Both were required by statute to be sentenced also to a term of PRS (see Penal Law § 70.06 [6]; § 70.45). However, as happened in a number of cases before our decisions in Matter of Garner v New York State Dept. of Correctional Servs. (10 NY3d 358 [2008]) and People v Sparber (10 NY3d 457 [2008]), the sentencing court failed to impose the PRS term. DOCS nevertheless included PRS in its record of each man’s sentence—a practice we decided in Garner was unlawful.
Joseph completed his prison sentence in August 2006, and Humberto completed his in January 2007. Both men began their improperly-imposed PRS terms—not in the community, but in a psychiatric hospital. Mental Hygiene Law article 10 had not then been enacted, but Joseph was involuntarily committed to a hospital under article 9 of the Mental Hygiene Law (Mental Hygiene Law § 9.27), and Humberto committed himself voluntarily, also under article 9 (Mental Hygiene Law § 9.13). Both, while in the hospital, violated the terms of their PRS—Joseph *131by trying to escape, Humberto by assaulting a fellow patient— and both were returned to prison.
Article 10, which created a new procedure for the confinement of sex offenders on the expiration of their prison terms, became effective on April 13, 2007. At first the State took no action under the new statute in either Joseph’s or Humberto’s case, presumably because there seemed no imminent prospect that either would be released. But our April 2008 decision in Garner changed that, making clear that the PRS terms that had allowed the State to reincarcerate Joseph and Humberto were unlawful. Correction Law § 601-d and Penal Law § 70.85, enacted in response to Garner and Sparber and effective June 30, 2008, effectively give prosecutors in such cases a choice either to seek resentencing or to forgo PRS, and in the autumn of 2008 the prosecutors in Joseph’s and Humberto’s cases chose the latter option. Faced with the prospect that the men would soon be freed, the State began article 10 proceedings, asking that each man be found “a sex offender requiring civil management” and be held in custody past his scheduled release date.
Joseph and Humberto contended that article 10 did not apply to them. They asserted that they were not “detained sex offenders” within the meaning of that article, because their PRS terms, and thus their imprisonment resulting from violations of PRS conditions, were unlawful. Both succeeded below, using different procedural vehicles. Joseph, after his release from custody was stayed under article 10, began a habeas corpus proceeding, which Supreme Court dismissed; the Appellate Division reversed and granted the writ (People ex rel. Joseph II. v Superintendent of Southport Correctional Facility, 59 AD3d 921 [3d Dept 2009]). Humberto made a motion to dismiss the article 10 proceeding against him, which Supreme Court granted; the Appellate Division affirmed (Matter of State of New York v Humberto G., 65 AD3d 690 [2d Dept 2009]). We granted leave to appeal in both cases, and we now reverse.
II
As these cases illustrate, the State’s efforts to confine certain sex offenders whose prison terms have expired predate the enactment of Mental Hygiene Law article 10. The State formerly proceeded in a number of cases, as it did in Joseph’s, under Mental Hygiene Law article 9, which contains provisions for the involuntary admission to mental hospitals of people who are mentally ill and in need of involuntary care and treatment (see *132Mental Hygiene Law §§ 9.27, 9.31). We held, however, in State of N.Y. ex rel. Harkavy v Consilvio (7 NY3d 607 [2006] [Harkavy I]) that the State was required to proceed in such cases under Correction Law § 402, a statute applicable to prison inmates believed to be mentally ill, rather than the more general provisions of article 9.
Evidently believing that section 402 procedures were inadequate to protect the public, the Legislature responded to Harkavy I by enacting article 10, a statute specifically designed to deal with sex offenders who are completing their prison terms. The statute sets out procedures for determining whether a “detained sex offender” is a “sex offender requiring civil management”—a term defined as “a detained sex offender who suffers from a mental abnormality” (Mental Hygiene Law § 10.03 [q]). A subcategory of “sex offender requiring civil management” is a “dangerous sex offender requiring confinement”—i.e., one whose mental abnormality involves “such a strong predisposition to commit sex offenses, and such an inability to control behavior, that the person is likely to be a danger to others and to commit sex offenses if not confined to a secure treatment facility” (Mental Hygiene Law § 10.03 [e]; see Mental Hygiene Law §§ 10.05-10.08; § 10.03 [q]). In State of N.Y. ex rel. Harkavy v Consilvio (8 NY3d 645 [2007] [Harkavy II]), we decided that, as to the prisoners involved in Harkavy I, the new statute had superseded Correction Law § 402 and that future proceedings concerning those prisoners should be held under article 10.
Under article 10, a prisoner can be found to be a “sex offender requiring civil management” (and thus perhaps a “dangerous sex offender requiring confinement”) only if he or she is a “detained sex offender” (see Mental Hygiene Law § 10.03 [q] [“ ‘Sex offender requiring civil management’ means a detained sex offender who . . .”]). The main issue in these cases is whether Joseph and Humberto were detained sex offenders when the State began proceedings against them under article 10.
Mental Hygiene Law § 10.03 (g) defines “detained sex offender.” The part of the definition that is relevant to this case says:
“(g) ‘Detained sex offender’ means a person who is in the care, custody, control, or supervision of an agency with jurisdiction, with respect to a sex offense or designated felony, in that the person is . . . *133“(5) A person convicted of a sex offense who is, or was at any time after September first, two thousand five, a patient in a hospital operated by the office of mental health, and who was admitted directly to such facility pursuant to article nine of this title or section four hundred two of the correction law upon release or conditional release from a correctional facility . . . .”
Joseph and Humberto are clearly persons of the kind described in subsection (5). Both were patients in a hospital operated by the Office of Mental Health after September 1, 2005, and both were admitted to the hospital under Mental Hygiene Law article 9 “directly . . . upon release or conditional release from a correctional facility”—Joseph involuntarily and Humberto voluntarily. Humberto argues that subsection (5) applies only to involuntary patients, but the plain text of the statute contradicts that argument.
On its face, the introductory language of section 10.03 (g) also fits Joseph and Humberto. It is beyond dispute that, when the article 10 proceedings began, they were in fact in DOCS’s custody, and DOCS can be an “agency with jurisdiction” (see Mental Hygiene Law § 10.03 [a] [“ ‘(a)gency with jurisdiction’ . . . can include the department of correctional services”]). Nor can it be doubted that each man was confined “with respect to a sex offense.” Joseph and Humberto argue, however, that “custody” must mean lawful custody and that since their confinement was unlawful under Garner, the definition of “detained sex offender” cannot apply to them. We reject this argument.
No doubt it is often reasonable to read “custody” as implying “lawful custody.” Here, however, the statute is best read as making no distinction between those properly and improperly confined. To see why, it is helpful to remember that article 10, which applies only to “detained” sex offenders, is the result of our decision in Harkavy I, which drew a distinction between prison inmates and other people. The sex offenders on whose behalf Harkavy I was brought argued that Mental Hygiene Law article 9, which generally governs the commitment of mentally ill people to hospitals, could not be applied to them because they were prisoners, and therefore subject to the more specific provisions of Correction Law § 402 for commitment of “any person undergoing a sentence of imprisonment” (Correction Law § 402 [1]). Accepting that argument, we held that “the Legislature *134intended the procedures of Correction Law § 402 to be used to evaluate for commitment all imprisoned persons” (7 NY3d at 613 [emphasis added]). The prisoners in Harkavy I sought this result, apparently because they preferred section 402 procedures to those used under article 9; we referred in Harkavy I to section 402’s “attendant procedural requirements including court supervision, pretransfer notice and an opportunity to be heard within a reasonable period of time prior to the inmate’s proposed release date” (id. at 614).
If Joseph and Humberto had been involved in the Harkavy I litigation, they would likely have argued that they were persons “undergoing a sentence of imprisonment” within the meaning of section 402, despite the fact that their “imprisonment” violated the law. And that argument would have been plainly correct. The point of Harkavy I was that the Legislature enacted certain procedures specifically designed for the transfer of inmates from prisons to mental hospitals. There is no reason why people whose confinement violated the law should not have been treated the same way as other inmates. And there is no reason to suppose that the Legislature intended to treat them differently when it enacted article 10, which provided a new way of dealing with the prisoners affected by the Harkavy I decision.
It is true that the enactment of Mental Hygiene Law article 10 has made special procedures applicable to those in prison less desirable from the prisoners’ point of view. Now that the alternative to an article 9 proceeding is an article 10 proceeding, Joseph and Humberto are arguing, in substance, that the State must proceed against them under article 9 if at all—thus seeking to come within the statute that the prisoners in Harkavy I sought to escape. This change in the preference of prisoners seems to result, at least in part, from the unattractive prospect of being sent to a “secure” mental health facility—the consequence of being found a “dangerous sex offender requiring confinement” under article 10. But of course it is the Legislature’s preference, not the prisoners’, that controls. Just as we held in Harkavy I that the Legislature intended a distinction between prisoners and other people alleged to be mentally ill, we now conclude that the Legislature intended to draw a similar line between prisoners and non-prisoners when it enacted article 10. The legality of the prisoners’ custody is irrelevant in both situations.
There is no injustice in holding prisoners situated as Joseph and Humberto are to be within article 10’s scope. The point of *135the prisoner/non-prisoner distinction we recognized in Harkavy I is not that one group should be treated more or less favorably than the other, but that different situations may call for different procedures. Indeed, there is no apparent reason why the Legislature had to limit article 10 to “detained” sex offenders. It could equally well have subjected all people who had committed sex offenses and were thought to be mentally ill—including those living in the community—to the procedures described in article 10. It chose not to do so, perhaps because it thought article 9 procedures adequate to deal with sex offenders who are not detained, or perhaps because it thought that those who are detained present a more serious threat to public safety.
We do not decide here whether there are any valid constitutional objections to article 10. But assuming, as we must for present purposes, that it can be validly applied to lawfully detained prisoners, it can be applied with equal validity to those whose imprisonment resulted from a procedural error. We hold that such prisoners are within the statute’s coverage.
Ill
Our conclusion that Joseph and Humberto are “detained sex offenders” subject to article 10 disposes of the only issue raised in the Humberto G. case. In the Joseph II. case, one other issue requires brief attention.
Joseph argues that he was entitled to notice and an opportunity to be heard before the issuance of an order under Mental Hygiene Law § 10.06 (h) staying his release from DOCS’s custody. The State argues, and Joseph does not dispute, that this claim is now moot, since Joseph was released after the Appellate Division decision in his favor. Joseph suggests, however, that we should exercise our discretion to decide a moot controversy where the issue presented is significant, likely to recur, and, because it arises in situations of relatively brief duration, apt to evade review (see Matter of Hearst Corp. v Clyne, 50 NY2d 707 [1980]).
The State does not challenge Joseph’s assertion that the issue he raises is significant and likely to recur; it does dispute his claim that it will evade review. Without resolving that dispute, we decline to address the issue here. It is barely alluded to in Joseph’s habeas corpus petition; it was not discussed by either court below; and the State, as appellant in this Court, has not briefed or argued the merits of the question. If this issue is one that should be addressed by means of the mootness exception, it can be addressed in some other case.
*136Accordingly, in People ex rel. Joseph II. v Superintendent of Southport Correctional Facility et al., the order of the Appellate Division should be reversed, without costs, and the petition dismissed. In Matter of State of New York v Humberto G., the order of the Appellate Division should be reversed, without costs, and Humberto G.’s motion to dismiss the article 10 proceeding denied.