Texas Quarter Horse Association Texas Thoroughbred Association Texas Horsemen's Partnership Gillespie County Fair and Festivals Association, Inc.et Al. // American Legion Department of Texas v. American Legion Department of Texas, Temple Post 133 Kickapoo Traditional Tribe of Texas Thompson Allstate Bingo Supply, Inc. And Moore Supplies, Inc.// Texas Quarter Horse, 496 S.W.3d 175

Texas Racing Commission adopted 2014 "historical racing" rules; private parties who would be harmed sued under APA §2001.038 and the UDJA seeking declaratory relief that the rules exceeded the Commission's authority.
Several industry groups intervened as defendants below to defend the rules; they did not assert affirmative claims but opposed plaintiffs' summary-judgment evidence and arguments.
The district court granted plaintiffs' summary judgment, sustained certain objections made by intervenors, and entered a final judgment declaring the rules invalid; plaintiffs nonsuited other claims to render the judgment final.
The Commission elected not to appeal and later repealed the historical-racing rules in March 2016, consistent with the statutory obligation to repeal rules invalidated by a final judgment.
Intervenors (appellants) nevertheless filed a timely appeal and later conceded repeal mooted the controversy, but sought vacatur of the district court judgment rather than mere dismissal of their appeal.
Plaintiffs moved to dismiss the appeal for lack of subject-matter jurisdiction, arguing intervenors lacked appellate standing because the agency (the real party in interest) had not appealed and had surrendered defense of the rules.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether third-party intervenors have standing to appeal a district court judgment invalidating an agency rule when the agency declines to appeal	Intervenors argue their status as parties of record and §2001.901 (APA) authorize appeal; thus appellate jurisdiction was invoked until repeal rendered the case moot	Plaintiffs argue intervenors lack a justiciable interest to obtain relief because the agency has acceded to the judgment and intervenors cannot compel the agency to readopt or enforce the rule	Intervenors lacked appellate standing; appeal dismissed for want of subject-matter jurisdiction and district-court judgment left undisturbed
Proper remedy when an appeal is brought only by parties lacking standing and the underlying rule is later repealed	Intervenors: if the appeal was live, then repeal that moots the appeal triggers vacatur of the lower-court judgment and dismissal of the cause	Plaintiffs: because intervenors lacked standing, the appellate court should simply dismiss the appeal; vacatur rule for moot appeals does not apply to appeals filed by improper parties	Vacatur rule for cases that become moot on appeal does not apply where the appellate defect is lack of standing; remedy is dismissal of the appeal only, leaving the lower-court judgment intact

Heckman v. Williamson Cty., 369 S.W.3d 137 (Tex. 2012) (outlines Texas justiciability doctrines and standing principles)
Speer v. Presbyterian Children’s Home & Serv. Agency, 847 S.W.2d 227 (Tex. 1993) (apparent rule that appellate courts vacate judgments when a case becomes moot on appeal)
U.S. Bancorp Mortgage Co. v. Bonner Mall Partnership, 513 U.S. 18 (1994) (federal vacatur doctrine and equitable limits on vacatur when mootness arises)
Diamond v. Charles, 476 U.S. 54 (1986) (private intervenor lacks standing to defend a law when the state declines to appeal)
Karcher v. May, 484 U.S. 72 (1987) (appeal defective for lack of proper parties/standing cannot support vacatur relief)
United States v. Munsingwear, Inc., 340 U.S. 36 (1950) (origin of vacatur practice to clear judgments when review is prevented by happenstance)
State v. Naylor, 466 S.W.3d 783 (Tex. 2015) (appeal by improper party must be dismissed for lack of appellate standing)