The ruling by Colorado’s Supreme Court that former President Donald J. Trump is ineligible to be president again because he engaged in an insurrection has cast a spotlight on the basis for the decision: the Constitution’s 14th Amendment, which includes a clause disqualifying people who violated their oaths of office from holding government positions in the future.

Mr. Trump has vowed to appeal to the Supreme Court. It is dominated by a supermajority of six justices who emerged from the conservative legal movement, which values methods of interpretation known as textualism and originalism. Under those precepts, judges should interpret the Constitution based on its text and publicly understood meaning when adopted, over factors like evolving social values, political consequences or an assessment of the intended purpose of the provision.

Some of the major questions raised by the ruling — like whether it would need an act of Congress to take effect as well as the power of a state court to decide whether a federal candidate is qualified — do not turn on interpreting the clause’s text. But here is where textualism and originalism may come into play.

What is the disqualification clause?

The 14th Amendment was adopted in 1868 as part of the post-Civil War Reconstruction Era. To deal with the problem of former Confederates holding positions of government power, its third section disqualifies former government officials who have betrayed their oaths from holding office.

Specifically, the clause says that people are ineligible to hold any federal or state office if they took an oath to uphold the Constitution and then engaged in insurrection or rebellion against the United States or aided its enemies. The clause also says a supermajority vote in Congress could waive such a penalty.

Is the president an ‘officer of the United States’?

Mr. Trump is unique among American presidents: He has never held any other public office and only swore an oath to the Constitution as president. That raises the question of whether the disqualification clause covers the oath he took. While as a matter of ordinary speech, a president is clearly an “officer of the United States,” there is a dispute over whether it excludes presidents as a constitutional term of art.

In 2021, two conservative legal scholars argued that a president does not count as an officer of the United States. In 2021, two other conservative legal scholars concluded that Mr. Trump is ineligible for the presidency. In finding the opposite, the Colorado Supreme Court also cited evidence of people in the immediate post-Civil War era discussing the president as an officer of the government, while focusing on ordinary use of the term rather than treating it as a term of art.

Were the events of Jan. 6 an insurrection?

The question of whether “insurrection” aptly describes the events of Jan. 6 is another topic of debate, although it was not a major disagreement among judges in Colorado.

The Colorado Supreme Court’s four-justice majority found that the events were an insurrection, and that issue was not the basis of any of the three dissents. The lower-court judge who had rejected the lawsuit on the grounds that the president is not an “officer of the United States” had nevertheless found that the events of Jan. 6 constituted an insurrection.

Has Trump ‘engaged’ in an insurrection?

Even assuming the events of Jan. 6 were an insurrection, there remains the question of whether the actions of Mr. Trump — who did not himself storm Congress — amounted to engaging in an insurrection against the government or giving aid and comfort to its enemies. The House committee that investigated Mr. Trump’s attempt to subvert the 2020 election concluded that the events met the standard of an insurrection.

Still, the special counsel, Jack Smith, did not include inciting an insurrection in the charges he brought against Mr. Trump, and to date Mr. Trump has not been convicted of any crime in connection with his attempts to stay in office for a second term despite losing the election. Mr. Trump has argued that all his actions were protected by the Constitution.

What else have courts said about the clause and Jan. 6?

There has never before been a presidential candidate who is accused in court of being an oath-breaking insurrectionist, so there is no Supreme Court precedent solidly on point. Other politicians faced similar legal challenges in connection with the events of Jan. 6, 2021.

In early 2022, opponents of Representative Madison Cawthorn, a Trump-aligned Republican of North Carolina, filed a lawsuit to keep him from running for re-election based on what they described as his role in encouraging what became the Jan. 6 riot. A Federal District Court judge dismissed the case, ruling that the clause no longer had force after the 1872 amnesty law. But an appeals court overturned the ruling, holding that the amnesty law was only retrospective and the prohibition still applied in general. Mr. Cawthorn lost his primary election, so the case was rendered moot without resolving other issues.

Opponents of Representative Marjorie Taylor Greene, a Trump-aligned Republican of Georgia, similarly tried to keep her from running for re-election in 2022. A state judge rejected that challenge, finding no persuasive evidence that she “took any action — direct physical efforts, contribution of personal services or capital, issuance of directives or marching orders, transmissions of intelligence, or even statements of encouragement — in furtherance” of what turned into the Jan. 6 riot after she first took the oath on Jan. 3, 2021. And in September 2022, a state judge in New Mexico ordered Couy Griffin, a commissioner in New Mexico’s Otero County, removed from office under the clause. Mr. Griffin had…