concurring.
We are asked to decide whether the State of Kansas may require members of a Kansas Indian tribe to register and title their vehicles with the State if they drive off-reservation on Kansas roads and highways. The majority decides this question by engaging in a balancing test pursuant to White Mountain Apache Tribe v. Bracker, 448 U.S. 136, 151, 100 S.Ct. 2578, 65 L.Ed.2d 665 (1980). It balances the Prairie Band’s sovereignty interests and related interests in “strong tribal economic development, self-sufficiency, and self-governance” against the State of Kansas’s interest in “public safety.” Op. at 1023-24. I am not sure what to think of this balance between incommensurate interests. It reminds me of asking whether a stick is longer than a rock is heavy. Cf. Bendix Autolite Corp. v. Midwesco Enterprises, Inc., 486 U.S. 888, 897, 108 S.Ct. 2218, 100 L.Ed.2d 896 (1988) (Scalia, J., concurring). I confess I suspect the argument is really about revenue, which both sides deny.
Fortunately, no such balancing is required. Because the issue here is the regulatory authority of the State over activity by tribal members outside the reservation, the proper analysis is not the balancing test of Bracker, which applies to attempts by state governments to regulate or enforce laws on Indian reservations, but that set forth in Mescalero Apache Tribe v. Jones: “Absent express federal law to the contrary, Indians going beyond reservation boundaries have generally been held subject to nondiscriminatory state law otherwise applicable to all citizens of the State.” 411 U.S. 145, 148-49, 93 S.Ct. 1267, 36 L.Ed.2d 114 (1973); see also Nevada v. Hicks, 533 U.S. 353, 362, 121 S.Ct. 2304, 150 L.Ed.2d 398 (2001) (restating these principles in the criminal context).
The majority applies the Bracker balancing test on the ground that “the activity *1029at issue in this case, licensing and titling of vehicles, takes place on the reservation.” Op. at 1022. I cannot agree. The State of Kansas has not attempted to project its jurisdiction over the on-reservation activities of the tribal vehicle registration and titling office. As the majority notes, “No one disputes the Tribe’s authority to apply the [Prairie Band Motor Vehicle Code] on reservation land.... ” Op. at 1020. The sole issue in the case is whether, when tribal members drive their vehicles off reservation onto Kansas roads, this can be regulated by the State.
If a tribe purported to issue “indulgences” allowing motorists to exceed the speed limit on Kansas highways, and an indulgence holder claimed that it preempted the Kansas traffic laws, no one would say the activity at issue is that of the tribal office of indulgence-granting. It is speeding on Kansas roads. For the same reason, it seems beyond question that this case is about the authority of the State over “Indians going beyond reservation boundaries,” and not about an attempt by the State to regulate activities taking place within the quasi-sovereign reservation lands of the Prairie Band. Mescalero, 411 U.S. at 148, 93 S.Ct. 1267.
The majority adopts this approach in the apparent belief that this panel is bound, under principles of law of the case, by the analysis in Prairie Band of Potawatomi Indians v. Pierce, 253 F.3d 1234 (2001) (Prairie Band I).1 See Op. at 1020 (“[W]e squarely addressed this issue in Prairie Band I and held that the Bracker balancing test applies in this case.”); see also id. at 1018 (describing the argument as resting on “the law of the case doctrine”). In Prairie Band I, we affirmed the district court’s grant of a preliminary injunction against Kansas’s enforcement of its vehicle registration and titling requirements against vehicles registered and titled by the Prairie Band.
Prairie Band I was hot a decision on the merits; it held only that the plaintiffs argument raised “questions going to the mérits ... so serious, substantial, difficult, and doubtful as to make the issue ripe for litigation and deserving of more deliberate investigation.” Prairie Band I, 253 F.3d. at 1257 (quoting Federal Lands Legal Consortium v. United States, 195 F.3d 1190, 1195 (10th Cir.1999)) (ellipsis in original). That was all it took to justify the preliminary injunction. Prairie Band I did not, as the majority contends, hold “that the Bracker balancing test applies in this case.” Op. at' 1020. Three times— once before, once after, and once in the middle of its discussion of the likelihood of success on the merits — the Prairie Band I opinion stressed that the tribe only had to prove, and thus the Court only had to decide, the more limited question of whether there were serious, substantial, difficult, and doubtful questions going to the merits. Prairie Band I, 253 F.3d. at 1253, 1255, 1257. That was in keeping with the Supreme Court’s admonition that it is improper to “equate[] ‘likelihood of success’ with ‘success’ ” in the context of a preliminary injunction ruling. University *1030of Texas v. Camenisch, 451 U.S. 390, 394, 101 S.Ct. 1830, 68 L.Ed.2d 175 (1981). “[T]he findings of fact and conclusions of law made by a court granting a preliminary injunction are not binding at trial on the merits.” Id. at 395, 101 S.Ct. 1830. It follows that law of the case doctrine does not apply, and this panel is not bound.
Contrary to Kansas’s arguments, however, application of Mescalero does not result in victory for the State. The Mescalero standard provides that tribal members are subject to non-discriminatory state laws when they are not on reservation lands. Mescalero, 411 U.S. at 148-49, 93 S.Ct. 1267. The question, then, is whether Kansas’s registration and titling policy is nondiscriminatory.
Kansas law broadly permits residents of other jurisdictions to drive their vehicles on Kansas roads if their vehicles are “duly licensed” in their own “state of residence,” provided that the driver’s jurisdiction permits vehicles registered in Kansas to drive on its roads. See Kan. Stat. Ann. § 8-138a. For purposes of this reciprocity statute, “ ‘state’ means a state, territory or possession of the United States, the District of Columbia, the Commonwealth of Puerto Rico, a foreign country and a state or province of a foreign country.” Kan. Stat. Ann. § 74-4305. Thus, residents of Missouri, Newfoundland, or Singapore can drive on Kansas roads without being forced to register their cars in Kansas, provided each jurisdiction extends equal hospitality to Kansas drivers. Indeed, Kansas even recognizes vehicles licensed by Indian tribes from outside of Kansas. In State v. Wakole, 265 Kan. 53, 959 P.2d 882, 883 (1998), the Kansas Supreme Court determined that tribally registered vehicles from Oklahoma were “duly licensed in the state of residence” because Oklahoma recognized the tribal registrations.
It is undisputed in this case that the Prairie Band permits Kansas residents to drive on the reservation in vehicles registered and titled in Kansas. It thus appears that out of the universe of non-Kansas vehicles that appear on Kansas highways, the State recognizes and is willing to accept registration and titling by the driver’s jurisdiction of residence, subject only to a requirement of reciprocity, except in the case of Kansas-based Indian tribes. That is a form of discrimination.
The State argues that public safety concerns justify this differential treatment, focusing particularly on the failure of the Prairie Band to include its vehicle registrations in the national criminal database. See Prairie Band I, 253 F.3d at 1251. As this Court acknowledged at the preliminary injunction stage, that is a “legitimate concern.” Id. But it raises the question: Does Kansas refuse to recognize registrations from other jurisdictions that, like the Prairie Band, are not linked to the national criminal database? If nonparticipation in the database is a genuine problem, Kansas could amend its reciprocity statute to recognize only those non-resident registrations that are included in the database, or meet other non-discriminatory public safety criteria. That would present a different case. Under the present statute, however, Kansas appears to be imposing on residents of Kansas-based reservations a requirement that it does not impose on residents of any other jurisdiction.2
*1031This analysis comports with the Ninth Circuit’s approach in Cabazon Band of Mission Indians v. Smith, 388 F.3d 691 (9th Cir.2004). That case addressed whether California’s refusal to permit tribal law enforcement vehicles to display emergency light bars was a discriminatory application of state law because California permits law enforcement vehicles from bordering states to display and operate emergency light bars within fifty miles of the border. Id. at 698-99. The court determined that tribal law enforcement agencies are similarly situated to the law enforcement agencies of bordering states. Id. at 699-700. Because there was no discernible reason for exempting law enforcement vehicles from bordering states from the emergency light bar rules, but not tribal enforcement vehicles, the court held that California was applying state law in a discriminatory manner. Id. at 700-01.
In this case, Prairie Band vehicles are similarly situated to vehicles licensed in jurisdictions outside of Kansas. Kansas recognizes these foreign vehicles without reference to any safety standards. By invoking a safety rationale for refusing to recognize Prairie Band vehicles, Kansas treats similarly situated parties differently. This is a discriminatory application of state law that violates the Mescalero standard. It is for this reason that the tribe should prevail. It is no disparagement of Congress’s undoubted “mandate to encourage tribal self-government and economic development” (Op. at 1026), to recognize that in this case the tribe should prevail not on the basis of a balancing test designed for state regulation of on-reservation activities, but rather on the basis of the discrimination test applicable to state regulation of the off-reservation conduct of tribal members. I respectfully concur.
. As an additional reason to adhere to the Bracker analysis, the majority states that "neither party briefed or argued the discrimination issue or provided any reason (other than Nevada v. Hicks) to abandon the sound Prairie Band I reasoning.” Op. at 1026. To the contrary, appellants strenuously argued in this Court that the Mescalero discrimination test, rather than Bracker balancing test, applies to this case. Br. of Appellants, at 28-31; see also Br. of Appellees, at 24-30 (responding to the argument). To be sure, the appellants failed to offer a persuasive argument why they should prevail under the Mescalero test. As their opponents pointedly observed: "they utterly fail to account for [Mescalero’s ] indication that state laws cannot discriminate against Indians off-reservation.” Id. at 43.
. A similar discrimination analysis might apply to any interest it may have in generating revenue by requiring members of Kansas tribes to register their vehicles with the State — an interest hinted at by the State’s brief in this Court. See Br. of Appellants, at 25. According to the brief, Kansas exempts tribal members from paying personal property tax on their vehicles, but imposes a flat fee "tailored ... to the amount of actual off-reservation use.” Id. Kansas does not charge such a fee to other non-resident drivers. *1031However, counsel for the State appeared to waive any consideration of the interest of the state in revenue generation from vehicle licensing, so a detailed analysis of this argument is not necessary. Oral Arg. Transcript, Sept. 29, 2004.