Most discussions of judicial deference to administrative agencies center on federal doctrines like those established in the Chevron and Auer cases. But there have been a lot of recent developments regarding deference and the separation of powers at the state level. Over the past several years, seven state supreme courts have rejected deference to the statutory or regulatory interpretations of state agencies. These state courts have suggested that such deference is incompatible with the duty of the judiciary to “say what the law is.” But until recently, none of the state courts that rejected deference had been asked to determine whether a law expressly requiring that the judiciary defer to an agency’s interpretation was unlawful.
In HWCC-Tunica, Inc. v. Mississippi Dep’t of Revenue, the Mississippi Supreme Court addressed that question head-on and determined that a statute requiring the judiciary to defer to the Department of Revenue’s statutory interpretations was incompatible with the Mississippi Constitution.
In HWCC-Tunica, two Mississippi casinos had developed rewards programs which allowed members to gain entries in a randomized prize drawing through frequently patronizing the casino. The casinos deducted the cost of the prizes from their gross revenues when calculating state income taxes, under an exemption for payouts made as a “result of a legitimate wager.” The Department concluded that this deduction was improper under a Department regulation providing a specific list of things that would qualify as a “legitimate wager.” The trial court deferred to the Department’s regulation and ruled in its favor. The casinos appealed, arguing that deference was incompatible with the Mississippi Constitution and with the Mississippi Supreme Court’s decision in King v. Mississippi Military Dep’t, in which the court had abandoned deference to agency statutory interpretations.
After dispensing with some preliminary arguments concerning argument preservation, the court concluded that the law requiring deference to the Department was incompatible with the Mississippi Constitution because “when deference is given to an agency interpretation, [the courts] share the exercise of the power of statutory interpretation with another branch in violation of Article I, Section 2” of the state constitution. The court concluded that this principle “is applicable to any case in which an agency interprets a statute” because “[i]nterpreting statutes is reserved exclusively for courts.”
Because the trial court had deferred to the Department’s regulation rather than conduct its own independent analysis of the key statutory terms, the court found that it had erred by failing to conduct a de novo review.”
Nevertheless, the court ultimately ruled in favor of the Department after conducting its own statutory analysis. Because state law described random drawings as “promotional activity” rather than a “gambling game,” the court concluded that the casinos could not deduct the cost of prizes as a loss. The court therefore affirmed the decision granting summary judgment to the Department.
Even though the Department ultimately prevailed, HWCC-Tunica is a significant decision. It makes Mississippi the first state, to my knowledge, to invalidate a legislature’s express effort to require judicial deference to an agency interpretation. As such, this decision can be read as a declaration of judicial independence, not only from executive agencies, but also from the legislative branch. According to the Mississippi Supreme Court, neither the legislature nor the executive can interfere with the judiciary’s exercise of its duty to “say what the law is.” And although Mississippi is the first, it is unlikely to be the last to reach that conclusion.
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 In re Complaint of Rovas Against SBC Michigan, 482 Mich. 90, 111, 754 N.W.2d 259, 272 (2008); Bowen v. State, Dep't of Transp., 2011 WY 1, ¶ 7, 245 P.3d 827, 829 (Wyo. 2011); Douglas v. Ad Astra Info. Sys., L.L.C., 296 Kan. 552, 559, 293 P.3d 723, 728 (2013); Hughes Gen. Contractors, Inc. v. Utah Labor Comm'n, 2014 UT 3, ¶ 25, 322 P.3d 712, 717; Ellis-Hall Consultants v. Pub. Serv. Comm'n, 2016 UT 34, ¶ 31, 379 P.3d 1270, 1275; Tetra Tech EC, Inc. v. Wisconsin Dep't of Revenue, 2018 WI 75, ¶ 42, 382 Wis. 2d 496, 535, 914 N.W.2d 21, 40; King v. Mississippi Military Dep't, 245 So. 3d 404, 407 (Miss. 2018). Myers v. Yamato Kogyo Co., Ltd., 220 Ark. 135 (2020).
 Marbury v. Madison, 5 U.S. 137, 178 (1803).
 296 So. 3d 668 (Miss. 2020)
 Id. ¶ 19. The statute, Miss. Code Ann. § 27-77-7(5), reads, “[a]t trial of any action brought under this section, the chancery court shall give no deference to the decision of the Board of Tax Appeals, the Board of Review or the Department of Revenue, but shall give deference to the department's interpretation and application of the statutes as reflected in duly enacted regulations and other officially adopted publications.”
 Id. ¶ 42 (quoting Mississippi Code Section 75-76-193).
 Id. ¶ 39.
 245 So. 3d 404, 408 (Miss. 2018)
 Id. ¶ 33 (quoting King, 245 So. 3 at 408). Article I, Section 2 states that “[n]o person or collection of persons, being one or belonging to one of these departments, shall exercise any power properly belonging to either of the others.”
 Id. ¶34.
 Id. ¶40.
 Id. ¶ 47.
 Id. ¶¶ 34-36.