NEW YORK – Like no one before him, Donald Trump is at once a former president, a leading candidate to be nominated for the presidency again and a criminal defendant.

He faces 91 felony charges in four separate cases for conduct before, during and after his presidency, including conspiring to defraud the United States in his efforts to overturn his 2020 election loss, mishandling classified documents and falsifying business records to cover up hush money to an adult film actress.

This unprecedented situation raises questions that previously would have been implausible law school hypotheticals.

One of those questions, about Trump’s eligibility to run again, moved from theoretical to real when the Colorado Supreme Court ruled him ineligible for that state’s primary ballot.

Is someone convicted of a crime eligible to serve as president?

Generally speaking, yes. The US Constitution says the president must be at least 35 years old, a natural-born citizen and a 14-year resident of the US; a clean criminal record is not a job requirement.

The 14th Amendment of the Constitution, adopted after the Civil War and little-discussed for decades, does block from public office anyone who has “engaged in insurrection or rebellion” against the US.

Trump was not charged with insurrection or rebellion.

Still, many Americans say those terms apply to what happened on Jan 6, 2021, when a violent pro-Trump mob attacked the US Capitol as Congress was certifying the results of the 2020 election.

The attack followed a rally at which Trump repeated his false claims that the election had been fraudulently stolen from him.

Does the 14th Amendment make Trump ineligible to serve again?

The question gained new prominence in August, when two conservative law professors, Mr William Baude and Mr Michael Stokes Paulsen, published a lengthy article arguing that it does.

The amendment constitutes “an immediate disqualification from office, without the need for additional action by Congress”, and “can and should be enforced by every official, state or federal”, who decide which candidates qualify for election ballots, they wrote.

Activists filed lawsuits in a number of states, including Minnesota, Colorado, Virginia and Michigan, seeking to apply the prohibition to keep Trump’s name off Republican primary nominating ballots and, should Trump win the party nomination, off the Nov 5, 2024 general election ballot.

In November, the Minnesota Supreme Court dismissed such an effort in regard to the state’s presidential primary. Then on Dec 19, the Colorado Supreme Court ruled by a vote of 4-3 that Trump is disqualified from being on the state’s primary ballot.

What does the Colorado ruling mean?

The court delayed it taking effect so that Trump has time to appeal to the US Supreme Court, which has been seen as the inevitable arbiter of whether the 14th Amendment applies.

Trump plans to immediately appeal to the Supreme Court – three of whose nine justices he appointed – and to seek a stay preventing the ruling from taking effect, according to a statement from his campaign.

Should the Supreme Court ultimately side with Colorado’s high court, other states could be expected to disqualify Trump as well.

Could Trump, as president, pardon himself?

Not if he is convicted on state charges such as those he faces in New York and Georgia. That is because the president’s constitutional power to “grant reprieves and pardons for offences against the United States”, applies only to federal crimes.

As for the dozens of counts he faces in two federal prosecutions, legal scholars disagree on whether the president can self-pardon.

Some point to the advice given by the Justice Department’s Office of Legal Counsel to president Richard Nixon in 1974 in connection with the Watergate scandal: “Under the fundamental rule that no one may be a judge in his own case, the president cannot pardon himself.”

Could Trump, while president, be sent to prison?

This is also unclear. There is an argument that the president’s responsibilities would override the imperative to serve a prison sentence.

“Constitutionally, you’d have a pretty good argument that you would have to let him out while he’s president,” said law professor Brian Kalt, from Michigan State University, who wrote a 2012 book that anticipated some of the current constitutional quandaries.

Could Trump be president from prison?

The logistical and security hurdles presented by a president behind bars boggle the mind.

If it came to that, the 15 department heads who make up the presidential Cabinet could declare the president “unable to discharge the powers and duties of his office” under the terms of the Constitution’s 25th Amendment and temporarily assign authority to the vice-president.

But, as Prof Kalt writes, that amendment is mainly viewed as applicable only if a president is “completely incapacitated” by, say, a stroke or severe dementia.

If elected, could Trump be removed by (another) impeachment?

In the last days of his presidency in January 2021, lawmakers unsuccessfully pursued an impeachment charge against Trump for inciting the insurrection at the Capitol.

In the event Trump wins the presidency again, lawmakers could try once more to force his removal by arguing that his conduct related to Jan 6 meets the constitutional standard of “high crimes and misdemeanours”.

Trump’s defenders would surely argue that his previous acquittal settled that issue.

Any new impeachment approved by the House of Representatives would, like the last one, face a steep uphill battle to achieve the supermajority vote in the Senate required to remove a president from office.

Does the Constitution offer Trump any defences?

Among other possible defences, including that Trump’s false statements about the 2020 election were protected by the First Amendment, Trump’s legal team has contended that his post-election activities, including efforts to overturn his defeats to President Joe Biden in battleground states, were official acts that are immune from prosecution.

Though the Constitution does not directly address the issue, the Supreme Court in the past has held that presidents are entitled to sweeping protection over actions they took within the “outer perimeter” of their official duties. But that was about immunity from civil lawsuits.

Since Trump is the first former president to face federal charges, claims of immunity from criminal prosecution are uncharted territory. BLOOMBERG