https://www.lawfaremedia.org/article/what-the-supreme-court-got-wrong-in-the-trump-section-3-case

Under the Court’s approach, only Congress has the power to determine which people are to be disqualified and under what procedures—at least when it comes to candidates for federal office and officials holding those offices. The majority claims that Congress’s Section 5 power to enact “appropriate” legislation enforcing the 14th Amendment is the exclusive mode of enforcing Section 3.

There are several flaws in the Court’s analysis. The most basic is that there is no good reason to believe that Section 5 is the exclusive mode of enforcing Section 3. As the Colorado Supreme Court emphasized in its ruling, Section 5 empowers Congress to enforce not just Section 3 but also every other part of the 14th Amendment, including its protections against racial and ethnic discrimination, the Due Process Clause, and more. These other provisions are considered to be self-executing, under long-standing federal Supreme Court precedent. Section 5 legislation is not the exclusive mode of enforcement for these other parts of the amendment.

Thus, state governments and federal courts can enforce these provisions even in the absence of congressional Section 5 enforcement legislation. Otherwise, as the Colorado Supreme Court notes, “Congress could nullify them by simply not passing enacting legislation.” Why should Section 3 be any different? Monday’s Supreme Court decision doesn’t give us any good answer to that question.

As the Supreme Court ruling notes, following its landmark precedent in City of Boerne v. Flores (1997), Congress’s Section 5 power is “remedial” in nature: It must be “congruent and proportional” to violations of the amendment it is intended to remedy. If Section 5 legislation is remedial in nature, including when it comes to enforcing Section 3, that implies some other entity—state governments and federal courts—has the initial responsibility for ensuring compliance with Section 3. The role of Section 5 is to remedy violations of that duty, not to be the exclusive enforcement mechanism.