The opinion of the court was delivered by: Justice Thomas
Docket No. 93978-Agenda 37-September 2002.
Plaintiffs, Joseph E. Birkett, State's Attorney of Du Page County, on behalf of the People of the State of Illinois, the County of Du Page, the Village of Bensenville, the City of Elmhurst, and the City of Wood Dale, filed a two-count amended complaint seeking (1) a declaration that the City of Chicago was constructing certain improvements at O'Hare International Airport in violation of the Illinois Aeronautics Act (Act) (620 ILCS 5/1 et seq. (West 2000)); and (2) an order enjoining the further construction of any such improvements until such time as the City complied with the Act. The circuit court of Du Page County entered summary judgment in the City's favor and denied plaintiffs' motion for partial summary judgment and injunctive relief. In addition, the trial court denied the request of United States Congressman Henry J. Hyde and State Senator James "Pate" Philip to intervene as plaintiffs. Plaintiffs appealed, and the appellate court concluded that entry of summary judgment in the City's favor was erroneous. 329 Ill. App. 3d 477. We granted the City's petition for leave to appeal. 177 Ill. 2d R. 315(a). In addition, we allowed the submission of several amicus curie briefs supporting both the City and plaintiffs. 155 Ill. 2d R. 345.
Section 47 of the Act (620 ILCS 5/47 (West 2000)) prohibits a municipality from making "any alteration or extension of an existing airport *** for which a certificate of approval has not been issued by the [Illinois Department of Transportation (IDOT)]." As the owner and operator of O'Hare International Airport, the City routinely undertakes a wide variety of projects designed to improve airport facilities. These projects generally fall into one of three categories: (1) "airfield" development, which includes runways, taxiways, aprons, hold pads, cargo areas, hangars, and other areas designed to facilitate the movement of aircraft; (2) "terminal" development, which includes terminals, concourses, and other areas designed to facilitate the movement of people through the airport; and (3) "landside" or "ground transportation" development, which includes roadways, parking facilities, mass transit, and other facilities designed to facilitate the movement of vehicles to and from the airport terminals. The City admits that it previously has undertaken extensive terminal and ground transportation improvements at O'Hare without first obtaining a certificate of approval from IDOT and that it intends to continue undertaking such improvements in the future. These improvements include new and renovated terminals, renovated concourses, new and renovated roadways, and expanded parking facilities.
On December 22, 1995, plaintiffs filed a two-count amended complaint against the City. Count I, an action in quo warrantor, alleged that, in clear violation of section 47, the City was undertaking substantial terminal and ground transportation improvements at O'Hare without first obtaining a certificate of approval from IDOT. Specifically, count I alleged that the City "currently has under construction tens of millions of dollars of physical alterations to [O'Hare]" and "in the past has constructed, or plans to build several hundred million dollars of additional construction projects at O'Hare." Accordingly, plaintiffs sought both a declaration that the City's actions were without authority and an order prohibiting the City from "constructing current and proposed alterations at O'Hare" without first obtaining a certificate of approval from IDOT. Count II, which was brought specifically under the Act, incorporated all of the allegations of count I, adding that "the intended primary purpose of much of the recent, ongoing and planned construction at O'Hare Airport is to incrementally expand the capacity of the airport" both to the detriment of neighboring communities and without the approval of IDOT. Count II sought an order prohibiting the "continued construction of current and proposed piecemeal elements of Chicago's construction program at O'Hare" without first obtaining a certificate of approval from IDOT.
On December 16, 1996, the trial court allowed Congressman Hyde and State Senator Philip to intervene as plaintiffs. The trial court later vacated this decision, concluding that Congressman Hyde and Senator Philip did not have standing to intervene.
On June 6, 2000, the City filed a motion for summary judgment. Plaintiffs responded with a cross-motion seeking both partial summary judgment and an injunction against "further physical alterations at O'Hare until these alterations are submitted to the State for a certificate of approval, and the State has issued a certificate of approval." After hearing arguments and reviewing the parties' briefs, the trial court entered summary judgment in the City's favor and denied plaintiffs' motion in its entirety. In so ruling, the trial court explained that the phrase "any alteration or extension of an existing airport," as set forth in section 47, is ambiguous. After considering both the Act as a whole and the IDOT regulation construing section 47 (see 92 Ill. Adm. Code §14.640 (2000)), the trial court determined that section 47 requires IDOT certification only for those alterations and extensions that affect "flight safety, glide path, obstruction of approaches, and things of that matter." Because none of the projects targeted by plaintiffs' complaint in any way implicated such matters, the trial court concluded that IDOT certification for those projects was unnecessary.
Plaintiffs appealed, and the appellate court affirmed in part, reversed in part, and remanded. 329 Ill. App. 3d 477. Initially, the appellate court agreed with the trial court's conclusion that section 47 requires IDOT certification only for those projects that impact runways or flight patterns. 329 Ill. App. 3d at 484-85. The appellate court then held, however, that the City may not evade compliance with section 47's certification requirement by segmenting a comprehensive project that includes alterations to runways or flight patterns into a series of smaller pieces. Thus, because there is evidence in the record to suggest that the contested terminal and ground transportation improvements to O'Hare are but one component of an overall plan that includes new or reconfigured runways, the appellate court concluded that the entry of summary judgment in the City's favor was erroneous. 329 Ill. App. 3d at 485. The appellate court additionally held that (1) plaintiffs were not entitled to injunctive relief; (2) federal law does not preempt section 47's certification requirement; and (3) the trial court's refusal to allow Congressman Hyde and Senator Philip to intervene was not an abuse of discretion. 329 Ill. App. 3d at 486-491.
Three issues are presented for our review: (1) whether section 47 requires the City to obtain IDOT certification before undertaking the terminal and ground transportation improvements at issue; (2) if so, whether section 47's certification requirement is preempted by federal law; and (3) whether the trial court's refusal to allow Congressman Hyde and Senator Philip to intervene was an abuse of discretion. Before reaching these issues, however, we must briefly consider whether this case is appropriate for our review at this time.
Propriety of Supreme Court Review
Plaintiffs argue that, due to certain changes in the City's plans for terminal and ground transportation improvements at O'Hare, this case presently rests upon an uncertain factual foundation and therefore is inappropriate for review at this time. Specifically, plaintiffs point to a series of news reports suggesting that, since the appellate court filed its judgment in this case, the City has announced that the World Gateway Project, which encompasses many of the terminal and ground transportation projects at issue in this case, may not go forward as planned. According to plaintiffs, in light of the uncertainty concerning which, if any, portions of the World Gateway Project remain viable, any decision by this court at this time would be purely advisory. Plaintiffs therefore urge this court to dismiss this appeal and remand the cause for additional fact finding in accordance with the appellate court's opinion.
We decline plaintiffs' invitation to dismiss this appeal. First, the issue in this case has never turned upon knowing with certainty what terminal and ground transportation improvements the City seeks to undertake at O'Hare. Plaintiffs' complaint did not seek to enjoin only those terminal and ground transportation improvements at O'Hare that are part of the World Gateway Project, nor did plaintiffs' complaint identify with any degree of specificity what projects they were seeking to enjoin. Rather, plaintiffs' complaint sought to enjoin the City from "constructing current and proposed alterations at O'Hare," whatever those alterations might prove to be.
Second, in the course of this appeal, this court allowed the City to file an affidavit from John F. Harris, the first deputy commissioner of the City of Chicago department of aviation. In that affidavit, Harris testifies that, notwithstanding the World Gateway Project's uncertain future, the City still intends to undertake substantial improvement projects at O'Hare without seeking IDOT's approval, including the construction of a new terminal and the extension of an existing concourse. Thus, we know with certainty that the City still intends to undertake at least some of the improvements that plaintiffs' complaint seeks to enjoin.
Finally, if plaintiffs genuinely believed that the City no longer intends to undertake the terminal and ground transportation improvements targeted in plaintiffs' complaint, then plaintiffs need only dismiss their complaint to end this litigation. The fact that plaintiffs are instead seeking a dismissal of this appeal-and with it the preservation of the appellate court's decision on the merits-suggests that plaintiffs fully expect the City to proceed with at least some terminal and ground transportation improvements at O'Hare. For these reasons, we decline to dismiss this appeal.
Necessity of IDOT Certification
The central question in this case is whether the City must obtain IDOT certification before undertaking the terminal and ground transportation improvements at issue. This question is one of statutory construction, and our analysis is guided by familiar principles.
The fundamental rule of statutory construction is to ascertain and give effect to the legislature's intent. Michigan Avenue National Bank v. County of Cook, 191 Ill. 2d 493, 503-04 (2000). The best indication of legislative intent is the statutory language, given its plain and ordinary meaning. Illinois Graphics Co. v. Nickum, 159 Ill. 2d 469, 479 (1994). Where the language is clear and unambiguous, we must apply the statute without resort to further aids of statutory construction. Davis v. Toshiba Machine Co., America, 186 Ill. 2d 181, 184-85 (1999). If the statutory language is ambiguous, however, we may look to other sources to ascertain the legislature's intent. People v. Ross, 168 Ill. 2d 347, 352 (1995). A court will give substantial weight and deference to an interpretation of an ambiguous statute by the agency charged with administering and enforcing that statute. Bonaguro v. County Officers Electoral Board, 158 Ill. 2d 391, 398 (1994). Indeed, a reasonable construction of an ambiguous statute by the agency charged with that statute's enforcement, if contemporaneous, consistent, long-continued, and in concurrence with legislative acquiescence, creates a presumption of correctness that is only slightly less persuasive than a judicial construction of the same act. People ex rel. Watson v. House of Vision, 59 Ill. 2d 508, 514-15 (1974). A statute is ambiguous if it is capable of being understood by reasonably well-informed persons in two or more different ways. People v. Jameson, 162 Ill. 2d 282, 288 (1994). The construction of a statute is a question of law that is reviewed de novo. In re Estate of Dierkes, 191 Ill. 2d 326, 330 (2000).
The statute at issue in this case is section 47 of the Illinois Aeronautics Act, which states:
"It shall be unlawful for any municipality or other political subdivision, or officer or employee thereof, or for any person, to make any alteration or extension of an existing airport or restricted landing area, or to use or operate any airport or restricted landing area, for which a certificate ...