OPINION
Appellees, R. Brooks Hardee, Trustee of the Farmco Trust (Farmco Trust); Davenport, L.L.C., General Partner of VWC, Ltd. (VWC); and Clifford E. Morton (Morton), are landowners who challenge the City of San Antonio’s annexation of two tracts of land. Appellants City of San Antonio; Tim Bannwolf, Individually and as Chairman of the Annexation Committee of the City Council of San Antonio; Mario M. Salas, Individually and as a Member of the City Council of San Antonio; and Emil R. Moncivais, Director of the Department of Planning of the City of San Antonio (collectively “the City”), filed a plea to the jurisdiction, asserting appellees lacked individual standing to bring their claims. The trial court denied the plea, and the City filed this interlocutory appeal pursuant to Tex. Civ. PRAC. & Rem.Code Ann. § 51.014(a)(8) (Vernon Supp.2001). We affirm the trial court’s order in part and reverse in part.
Background
Appellees Farmco Trust and Morton own tracts of land in east Bexar County (the Foster Road Property) within a larger area designated by the City, for annexation purposes, as the Foster Meadows Area. Appellee VWC owns a tract of land in west Bexar County (the Potranco Road Property) included within a larger area designated by the City as the Potranco Road/FM 1604 Area. Both designated areas were annexed effective December 81, 2000.
Appellees filed suit before the effective annexation date claiming the City failed to comply with various statutory provisions. The City argues any improprieties in the annexation process are merely procedural irregularities, which may make the annexation voidable, but not void. Further, in its plea to the jurisdiction, the City claims the appellees have no individual standing to overturn the annexation because any challenges to the validity of an annexation proceeding must be brought as a quo war-ranto proceeding. See Tex. Civ. PRAC. & Rem.Code §§ 66.001, 66.002 (Vernon 1997). Appellees counter they have standing to pursue an individual, collateral attack on the annexation because the City acted wholly outside its authority, rendering the attempted annexation void. The trial court denied the plea to the jurisdiction without stating its reasons. 1
Appellees argue the trial court’s decision was correct because: (1) the City acted outside its authority by failing to adopt a required annexation plan under Tex. Loc. Gov’t Code Ann. § 43.052; (2) the City *210 acted outside its authority because it attempted to annex areas by resolution rather than by ordinance as required by the City Charter; and (3) the annexation of the Foster Road Area is void because it was undertaken in violation of the Texas Open Meetings Act. 2 Appellees also argue the City is estopped to challenge standing because the City entered into an agreed temporary order pending the outcome of the lawsuit. 3
Standard of Review
In reviewing the denial of the City’s plea to the jurisdiction, we take the factual allegations in the appellees’ trial court petition as true and construe them in favor of the appellees.
City of San Augustine v. Parrish,
Historically, review of an individual party’s standing to challenge annexation inquires whether the challenge attacks the city’s authority to annex the area in question or simply complains of some violation of statutory procedure.
See City of Wichita Falls v. Pearce,
Discussion
A. Tex. Loc. Gov’t Code § 43.052
“The Texas Constitution confers the power to annex territory on cities and
*211
the legislature has provided the scheme to be followed.”
Alexander Oil Co.,
In 1999, the Legislature adopted a new version of Texas Local Government Code section 43.052, entitled Municipal Annexation Plan Required, which reads in part as follows:
(b) A municipality may annex an area identified in the annexation plan only as provided by this section.
(c) A municipality shall prepare an annexation plan that specifically identifies annexation that may occur beginning on the third anniversary of the date the annexation plan is adopted. The municipality may amend the plan to specifically identify annexations that may occur beginning on the third anniversary of the date the plan is amended.
Tex. Loc. Gov’t Code Ann. § 43.052(b)-(c) (Vernon Supp.2001). Section 17 of the enabling legislation states:
(b) Each municipality shall adopt an annexation plan as required by Section 43.052, Local Government Code, as amended by this Act, on or before December 31, 1999, that becomes effective December 31,1999.
(c) Except as provided in Subsections (d)and (g) of this section, 4 the changes in law made by Sections 2 through 8 and 10 through 15 of this Act apply only to an annexation included in a municipality’s annexation plan prepared under Section 43.052, Local Government Code, as amended by this Act. Except as provided by Subsection (d) of this section, a municipality may continue to annex any area during the period beginning December 31, 1999, and ending December 31, 2002, under Chapter 43, Local Government Code, as it existed immediately before September 1, 1999, if the area is not included in the annexation plan, and the former law is continued in effect for that purpose.
Acts of May 30,1999, 76th Leg., R.S., ch. 1167, § 17(b)-(c), 1999 Tex. Gen. Laws 4090. (emphasis added).
Appellees argue that because the City did not adopt an annexation plan prior to December 31, 1999, the City may not continue to annex non-plan areas during the period of 12/31/99 through 12/31/02 under Section 17, Subsection (c) of the enabling legislation. Appellees contend Section 17 is a limitation on the City’s authority and, consequently, failure to adopt a plan by *212 December 31, 1999 makes the attempted annexation void.
Notice and hearing requirements are procedural limits on annexation not affecting the municipality’s authority to make the annexation.
Laidlaw Waste Sys.,
Appellees do not claim the property is outside the City’s authority to annex, only that the City did not follow the procedures set out in the new section 43.052(b)-(c). If the City’s attempted annexation is in violation of the statutory requirements, the annexation may be voidable and subject to being set aside by the court, but it is not void. Accordingly, appellees have no standing to challenge the annexation under Tex. Loc. Gov’t Code Ann. § 43 .052 but must seek a quo warranto action.
B. Violation of City Charter
In their next issue, appellees claim they have standing to challenge the annexations because the actions were carried out by resolution rather than ordinance in violation of the City Charter. However, ap-pellees’ brief states: “The challenged annexations were effected by two separate ordinances: one annexed an area in southeast Bexar County in which Plaintiffs Har-dee and Morton owned property, and the other annexed an area in west Bexar County in which Plaintiff VWC owns land.”
We may accept admissions made in the briefs as true.
Jansen v. Fitzpatrick,
C. Texas Open Meetings Act
Appellees Farmco Trust and Morton claim standing to sue under the Texas Open Meetings Act because they say the annexation of the Foster Road Area was accomplished by written memorandum rather than an authorized action of the City Council meeting in conformity with the Act. The Texas Open Meetings Act allows “an interested person” 7 to “bring an action by mandamus or injunction to stop, prevent, or reverse a violation or threatened violation of [the Open Meetings Act] by members of a governmental body.” Tex. Gov’t Code Ann. 551.142(a) (Vernon 1994). Actions by a City must comply with the Open Meetings Act or they are voidable. Tex. Gov’t Code Ann. § 551.141 (Vernon 1994).
The City argues that because a violation of the Open Meetings Act merely renders *213 the annexation voidable, the alleged defect does not implicate the City’s authority and is therefore only a procedural defect that must be challenged by quo warranto proceeding. The City does not attempt to reconcile the standing provision of the Open Meetings Act with the longstanding caselaw prohibiting individual challenges to annexation. 8
We presume statutes are “enacted by the legislature with full knowledge of the existing condition of the law and with reference to it.”
Williams v. Williams,
Additionally, there are public policy reasons for holding that an annexation action taken by a city should be subject to challenge for violation of the Open Meetings Act. The Open Meetings Act is designed to allow the public notice “concerning the transactions of public business.”
Toyah Indep. Sch. Dist. v. Pecos Barstow Indep. Sch. Dist.,
Thus we hold appellees Farmco Trust and Morton have standing to challenge the annexation of the Foster Road Area under the Open Meetings Act. We do not reach the merits of that claim in this interlocutory appeal.
D. Estoppel
Estoppel is an equitable doctrine which prevents a party from challenging the trial court’s jurisdiction because the party’s prior conduct is inconsistent with their claim of lack of jurisdiction.
Strunck v. Peoples,
Appellees claim the City is es-topped from challenging standing because the City acknowledged appellees’ standing to file suit when the parties entered an agreed temporary order allowing appellees to continue their prior use of the annexed property pending the outcome of the lawsuit. In fact, the appellees sought the temporary injunction and the City merely agreed to join the appellees in their request. The order outlines the parties’ understanding of the permitted uses of the land pending the outcome of the suit. 10 Nothing in the order or the record suggests the City agreed appellees pled facts sufficient to confer jurisdiction. The order recites that the parties wished to avoid a temporary injunction hearing, and by its own terms, the agreed order terminates at the end of the litigation. Because the order merely reflects the City’s agreement to maintain the status quo during the litigation, the joint request for an agreed order does not estop the City from challenging the appellees’ standing to bring suit as individuals.
Conclusion
Because we hold the appellees lack standing to challenge annexation based on procedural violations of Tex. Loe. Gov.Code Ann. § 43.062, the City Charter, and the City Code, we affirm only that part of the trial court’s order denying the plea to the jurisdiction based on R. Brooks Hardee, Trustee of the Farmco Trust, and Clifford E. Morton’s claims under the Texas Open Meetings Act and remand for further proceedings on the merits of the those allegations. We reverse the remainder of the trial court’s order.
Notes
. Following entry of the order denying the plea to the jurisdiction, the trial court entered findings of fact and conclusions of law that the appellees lack standing to challenge the annexation based on the City's alleged failure to comply with the Voting Rights Act. Appel-lees do not challenge this holding on appeal.
. In the trial court, appellees also argued: (1) the City failed to give proper notice to public schools and landowners; (2) there were numerous inadequacies and failures of notice regarding the inventory of proposed services and facilities for the annexed areas; and (3) the City failed to obtain preclearance of the annexation from the Justice Department. Ap-pellees do not contend on appeal that they have standing to bring these procedural types of claims.
. The City did not brief a response to the estoppel issue.
. Subsection (d) of section 17 outlines certain new procedural requirements that apply to annexations outside the annexation plan, where the first public hearing on the annexation is conducted on or after September 1, 1999. Subsection (g) makes Tex Loc. Gov’t Code Ann. § 43.0712 (regarding annexation of special districts) applicable to all annexations, regardless of date.
. The prior section 43.052 notice and hearing requirement still exists in an amended form but it moved to a different section number. Tex Loc. Gov’t Code Ann. § 43.0561 (Vernon Supp.2001) (former § 43.052 (Vernon 1997)).
. In the alternative, if appellees’ complaint is that the ordinances were untimely or are ineffective because the City did not adopt an annexation plan, those deficiencies are procedural defects under the Local Government Code as previously discussed.
.There is no assertion that Farmco Trust and Morton do not qualify as "interested persons.”
. We have not found nor have the parties cited any cases interpreting the standing provision of the Open Meetings Act in the context of an annexation challenge.
See, e.g., Laidlaw Waste Sys.,
. The standing provision was adopted along with the initial version of the Act in 1967.
See City of Abilene v. Shackelford,
. It is clear from the discussions at the hearing on the plea to the jurisdiction and the language of the agreed order that the City believed all or part of appellees’ current use of the land would be preserved (at least for a time) even if the annexation was valid. See Tex. Loc. Gov't Code Ann. § 43.002 (Vernon Supp.2001). Section 43.002 allows certain land uses to continue even after annexation.
