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 …