However troubling its political implications might be, the Colorado Supreme Court’s ruling on Tuesday that Donald Trump is disqualified from the state’s primary ballot for having “engaged in insurrection” demonstrates that the judicial system is still functioning in the United States. The reason is straightforward: The court applied the plain language of the Constitution, doing its job with clarity and fidelity to the rule of law.

But perhaps what is most striking about Colorado’s decision was the conservative reasoning the justices employed to reach their conclusion. The four justices who voted in the majority adhered to three stalwart principles of judicial conservatism: textualism (by which judges endeavor to strictly apply the plain text of the Constitution), originalism (by which they refer to historical sources for a contemporaneous understanding of that text), and federalism (by which judges take pains to respect the dual sovereignty of the states alongside the federal government as well as the state courts’ concomitant prerogative to construe their own laws).

This third element is perhaps the most interesting. The Colorado Supreme Court was tasked with interpreting Colorado’s Uniform Election Code of 1992, which contains that state’s criteria for getting on its presidential ballot. It determined that disqualification under Section 3 of the Fourteenth Amendment is also disqualifying under Colorado law. And it upheld the lower court’s conclusion, after a multiday evidentiary hearing, that Donald Trump in fact engaged in insurrection. Because he is thus disqualified as a matter of Colorado law, the Colorado Supreme Court determined, “it would be a wrongful act under the Election Code for the Secretary [of State] to list him as a candidate on the presidential primary ballot.”

[George T. Conway III: The Colorado ruling changed my mind]

The U.S. Supreme Court has ignored this sort of reasoning before—and to ill effect. In Bush v. Gore, it ruled in 2000 that manual recounts under Florida’s law regarding contested election results would violate the Constitution’s equal-protection clause, and thus effectively handed the election to George W. Bush by a margin of 537 votes. In dissent, Justice John Paul Stevens emphasized that “when questions arise about the meaning of state laws, including election laws, it is our settled practice to accept the opinions of the highest courts of the States as providing the final answers.” The conservative justices of today’s Court should bear this example in mind—and the stakes for the Court’s legitimacy—when considering whether the Colorado court got this aspect of its interpretation right.

Next, consider the plain language of the Fourteenth Amendment, which belies a handful of textual ambiguities: What is “insurrection” (and did January 6 qualify)? What does “engaged” mean (and did Trump do it)? And is the president of the United States an “officer” of the United States covered by Section 3? As for the first two questions, President Joe Biden summed things up yesterday, calling it “self-evident” that Trump “supported” an insurrection. Nobody seriously contends otherwise. The rebuttal instead is that Section 3 kicks in only if a jury makes these findings beyond a reasonable doubt pursuant to a federal statute that criminalizes insurrections (and which Special Counsel Jack Smith declined to invoke in indicting Trump)—an argument that one of the dissenting justices made as well.

The Colorado Supreme Court elegantly dispensed with that concern. Again, it applied a plain reading of the law, concluding that Congress’s decision to criminalize “the same conduct that is disqualifying under Section Three … cannot be read to mean that only those charged and convicted of violating the law are constitutionally disqualified from holding office without assuming a great deal of meaning not present in the text or the law.” Neither the Constitution nor the statute say anything of the sort. The court thus refused to go where it needn’t by theorizing about inferences buried beneath the plain text, which is precisely how conservative judging, at least in theory, is supposed to work.

On the officer question, the Colorado Supreme Court focused on the Constitution as written, noting that it “refers to the Presidency as an ‘Office’ twenty-five times,” including in connection with the natural-born-citizen eligibility requirement for the presidency (Article II, Section 5), the four-year cap on presidential terms in office (also in Article II, Section 5), and the impeachment clause (Article I, Section 3). It then turned to tools of originalism, observing, for example, that “dictionaries from the time of the Fourteenth Amendment’s ratification define ‘office’ as a ‘particular duty, charge or trust conferred by public authority, and for a public purpose,’ that is ‘undertaken by … authority from government or those who administer it.’” The court then reasonably concluded that “the Presidency falls comfortably within these definitions.” Judges make these kinds of interpretative decisions all the time.

Serious constitutional scholars have nonetheless pushed back on the notion that Section 3 applies to presidents, underscoring that prior drafts of Section 3 included references to “the office of the President” but that the language was ultimately abandoned. According to this argument, the framers of Section 3 intended only to prevent insurrectionists from serving in the Electoral College, but left qualified electors free to choose insurrectionists for the presidency. But those distinctions are missing from the actual text. As the conservative scholars William Baude and Michael Stokes Paulsen argued in an exhaustive article, “The substantive terms of Section Three’s prohibition are not themselves difficult or inscrutable.” Even more to the point: Jurists differ over what tools of constitutional interpretation are paramount in construing arcane constitutional terms. The political right, for example, has long assailed progressive judges for emphasizing the purposes behind a law when a plain-text reading would arguably suffice. For conservative justices to abandon that hierarchy now, on a case this consequential, would destroy whatever guise of impartiality the Court has left.

[David Frum: The Colorado Supreme Court just gave Republicans a chance to save themselves]

If the U.S. Supreme Court winds up leaving the Colorado Supreme Court’s decision undisturbed, it will inevitably get GOP voters and politicians very upset with the justices in the majority. It could also encourage states to play fast and loose with Section 3 to keep legitimate candidates off future ballots. But the threat of political retribution is just the sort of possibility that motivated the Framers of the original Constitution to give federal judges lifetime appointments under Article III—they needn’t think about the popularity of their decisions. Moreover, the ostensible point of the so-called conservative judicial philosophies of textualism, originalism, and federalism is to confine judges to the business of judging. That means resolving, on the narrowest possible grounds, discrete disputes affecting the immediate parties, at least one of whom is concretely injured by the other—rather than wading into political or normative policy conundrums in ways that aggrandize their own power relative to that of the other branches of government. If the purportedly conservative members of the U.S. Supreme Court are intellectually honest about their jurisprudential approach to the law, this case should not be hard.