Plaintiffs Citizens Addressing Reassignment and Education, Inc., Jade John Litcher, *826and Elizabeth Lee Haner filed suit to block defendant, the Wake County Board of Education ("the Board"), from building a modular school on property leased from the National Alumni Association of Dubois High School ("the Association"). Plaintiffs appeal from an order of the superior court granting the Board's motion to dismiss plaintiffs' claims on the grounds of mootness and laches. Since the school has already been opened, we agree with the trial court that most of plaintiffs' claims are moot. As to those claims that are not moot, plaintiffs have failed to state a claim for relief, and, therefore, we affirm.
Facts
The facts of this case are essentially undisputed. In an effort to alleviate school overcrowding, the Wake County Board of Commissioners, in November 2004, approved the opening of three modular elementary school facilities. These schools, scheduled to begin operating in August 2005, were to serve as temporary locations until the construction of permanent schools could be completed in 2006 and 2007. For one of the modular facilities-intended to hold approximately 500 students-the Board leased a parcel of Wake County real property ("the Dubois site") in March 2005 from the Association. The remaining two modular facilities were to be placed on land owned by the Board.
On 31 May 2005, plaintiffs sued the Board, alleging that the lease agreement and the Board's construction of the modular school on the leased Dubois site violated N.C. Gen. Stat. § 115C-521(d) (2005), which provides that "[l]ocal boards of education shall make no contract for the erection of any school building unless the site upon which it is located is owned in fee simple by the board[.]" Plaintiffs sought a declaratory judgment that the lease agreement was void; a permanent injunction and a writ of mandamus prohibiting the expenditure of any additional public funds for the construction of the modular facility on the leased premises; and an order requiring the Board to repay to the Wake County Board of Commissioners all public funds spent on lease payments and the modular facility's construction, as well as any payments that were otherwise made in violation of N.C. Gen.Stat. § 115C-521(d).
The Board filed a motion to dismiss plaintiffs' claims on 7 July 2005. Following a 29 July 2005 hearing, the trial court dismissed plaintiffs' claims, concluding that they were both moot and barred by the doctrine of laches. With respect to mootness, the court found that, at the time of the hearing, "the modular school facility . . . was substantially complete. Staff will report to the school building on or about August 15, 2005, and students will report on August 25, 2005." Based on this finding, the court concluded that "[i]n view of the relief requested by plaintiffs and the substantial completion of the school facility . . ., the case before the [c]ourt is moot." Further, based on findings of fact relating to when plaintiffs first became aware of the likely use of the Dubois site, the timing of their efforts to block the construction of the school, and the expense incurred by the Board, the court "in its discretion, . . . determined that the principle of laches should be invoked because of the delay in bringing this suit and the substantial harm to the Board of Education, and especially to those students who are to attend the school at the Dubois site, that would result if an injunction were granted." Plaintiffs have timely appealed to this Court from the order granting the Board's motion to dismiss.
Discussion
Plaintiffs included 24 assignments of error in their record on appeal and, in those assignments of error, specifically challenged both the trial court's conclusion that their claims were moot as well as the court's determination that the doctrine of laches also barred their claims. In plaintiffs' brief, however, their entire argument with respect to mootness was limited to the following single paragraph:
The [c]ourt below erred in alternatively holding that the case is moot. [Citation to the trial court's order]. As demonstrated *827in the preceding six (6) [a]rguments, [plaintiffs] are entitled to the issuance of a declaratory judgment, permanent injunction and writ of mandamus regarding [the Board's] violation of the clear and plain language of N.C. Gen.Stat. § 115C-521(d).
Nowhere, however, in plaintiffs' "preceding six" arguments do they address mootness or cite to any authority pertaining to that principle. Moreover, plaintiffs have not submitted to this Court any memorandum of additional authority, as permitted by N.C.R.App. P. 28(g), with respect to mootness.
In short, plaintiffs have submitted no authority in support of their contention that the trial court erred in concluding that their claims were moot. "Assignments of error not set out in the appellant's brief, or in support of which no reason or argument is stated or authority cited, will be taken as abandoned." N.C.R.App. P. 28(b)(6) (emphasis added). Plaintiffs have, therefore, abandoned their assignment of error to the trial court's dismissal of their claims based on mootness. See Goodson v. P.H. Glatfelter Co., 171 N.C.App. 596, 606, 615 S.E.2d 350, 358 ("It is not the duty of this Court to supplement an appellant's brief with legal authority or arguments not contained therein. This assignment of error is deemed abandoned. . . ."), disc. review denied, 360 N.C. 63, 623 S.E.2d 582 (2005). Nevertheless, pursuant to our discretion under N.C.R.App. P. 2 (permitting suspension of appellate rules to "expedite decision[s] in the public interest"), we elect to suspend the appellate rules and reach the merits of plaintiffs' mootness contentions as brought out in oral argument.
With respect to plaintiffs' efforts to obtain a permanent injunction and writ of mandamus prohibiting any additional expenditures for the modular school's construction, "`[i]t is quite obvious that a court cannot restrain the doing of that which has already been consummated.'" Fulton v. City of Morganton, 260 N.C. 345, 347, 132 S.E.2d 687, 688 (1963) (quoting Austin v. Dare County, 240 N.C. 662, 663, 83 S.E.2d 702, 703 (1954)). Although plaintiffs assigned error to the trial court's finding that as of "July 29, 2005, . . . the modular school facility . . . was substantially complete" and that "students will report on August 25, 2005," they have neither brought this assignment of error forward in their brief nor made any argument suggesting why it was not supported by competent evidence. This finding is, therefore, binding on appeal. See In re P.M., 169 N.C.App. 423, 424, 610 S.E.2d 403, 404 (2005) (factual assignments of error binding on appeal when appellant "failed to specifically argue in her brief that they were unsupported by evidence"). Consequently, as a permanent injunction and writ of mandamus would only attempt to stop that which has already been done, plaintiffs' claims for relief on these issues are moot. See Roberts v. Madison County Realtors Ass'n, 344 N.C. 394, 402, 474 S.E.2d 783, 789 (1996) (courts may not issue injunctions to "prohibit [events] from taking place when [they] ha[ve] already occurred").
Regarding plaintiffs' efforts to obtain a declaratory judgment that the construction of the modular school facility violates § 115C-521(d), actions filed under the Declaratory Judgment Act, N.C. Gen.Stat. §§ 1-253 through -267 (2005), are subject to traditional mootness analysis. Carolina Spirits, Inc. v. City of Raleigh, 127 N.C.App. 745, 747, 493 S.E.2d 283, 285 (1997), disc. review denied, 347 N.C. 574, 498 S.E.2d 380 (1998). "A case is considered moot when `a determination is sought on a matter which, when rendered, cannot have any practical effect on the existing controversy.'" Lange v. Lange, 357 N.C. 645, 647, 588 S.E.2d 877, 879 (2003) (quoting Roberts, 344 N.C. at 398-99, 474 S.E.2d at 787). Typically, "[c]ourts will not entertain such cases because it is not the responsibility of courts to decide `abstract propositions of law.'" Id. (quoting In re Peoples, 296 N.C. 109, 147, 250 S.E.2d 890, 912 (1978), cert. denied, 442 U.S. 929, 99 S.Ct. 2859, 61 L.Ed.2d 297 (1979)). The disputed school is already operating, and plaintiffs do not seek closure of the facility. Therefore, a legal determination declaring *828the building unlawful would have no practical effect on the controversy. This issue presents only an abstract proposition of law for determination and is, therefore, also moot.
As for plaintiffs' request for a declaratory judgment voiding the lease with the Association and for an injunction prohibiting future lease payments, we agree with plaintiffs that this issue is not necessarily moot. In seeking this relief, however, plaintiffs have relied upon an erroneous construction of N.C. Gen. Stat. § 115C-521(d).
Under this statute, "[l]ocal boards of education shall make no contract for the erection of any school building unless the site upon which it is located is owned in fee simple by the board[.]" N.C. Gen.Stat. § 115C-521(d) (emphasis added). Plaintiffs' contention that the lease with the Association violates this provision is contrary to the plain language of the statute. By its specific terms, the statute prohibits only contracts "for the erection" of school buildings. The lease agreement, however, is merely a contract to lease land.1
While the lease does state that the Board intended to use the Dubois site "for construction of an approximate 500 student modular school facility," this provision also specifies that "such use shall be undertaken in a manner that complies with applicable law as now or hereafter enacted or construed . . . ." Thus, even if plaintiffs are correct that erection of a modular facility on leased property violates N.C. Gen.Stat. § 115C-521(d)-an issue on which we express no opinion-nothing in the lease requires, or even permits, the Board to engage in conduct that would violate that statute.
The agreement with the Association is addressed only to standard landlord and tenant issues, including the duration of the tenant's leasehold, rent, and the obligations of the landlord and tenant. It contains no terms relating to the actual erection of any building. The statute at issue, however, does not prohibit leasing property; it prohibits the erection of a building. Accordingly, plaintiffs' claims seeking a declaration that the lease was void and an injunction prohibiting further lease payments were, therefore, properly dismissed.
Plaintiffs also sought, in their prayer for relief, an order that the Board "repay to the Board of Commissioners of Wake County all public funds that were expended for lease payments and expended for the purpose of building, constructing or erecting of any public school building on the leased [p]remises, and any other payment which were [sic] made in violation of N.C. Gen.Stat. § 115C-521(d)." In oral argument, plaintiffs contended, with respect to the lease payments, that this remedy was not barred as moot. Our determination that the lease did not violate § 115C-521(d), however, disposes of this contention.
As for repayment of other funds expended, plaintiffs did not, even in oral argument, provide any legal basis for requiring the Board to repay to Wake County funds spent on the building of the modular school building. Without plaintiff presenting a legal basis for awarding such relief, we cannot reverse the trial court. As our Supreme Court has stressed, "[i]t is not the role of the appellate courts . . . to create an appeal for an appellant." Viar v. N.C. Dep't of Transp., 359 N.C. 400, 402, 610 S.E.2d 360, 361 (2005) (per curiam).
Finally, plaintiffs sought a permanent injunction prohibiting the Board from making similar purportedly illegal contracts in the future. It is, however, well established that "[c]ompleted acts and past occurrences in the absence of any evidence tending to show an intention on the part of the defendants to [commit future violations], will not authorize the exercise of the court's injunctive power." State ex rel. Bruton v. Am. Legion Post, 256 N.C. 691, 693, 124 S.E.2d 885, 886-87 (1962). Plaintiffs have not assigned error to the trial court's following finding of fact: "There was no evidence *829presented to demonstrate [the Board] currently is planning or installing any other school facility on leased property and such is not at issue in this case. There was no evidence that the Board of Education has previously installed a school facility on leased property." This finding of fact, binding on appeal, supports the trial court's decision not to grant a permanent injunction barring future contracts by the Board potentially in violation of N.C. Gen.Stat. § 115C-521(d).
In sum, each of plaintiffs' claims is either moot or otherwise meritless. Because of our resolution of this appeal, we need not address the trial court's determination that plaintiffs' claims are barred by laches.
Affirmed.
Judge CALABRIA concurs.
Judge JACKSON concurs in part and dissents in part in a separate opinion.