When President-elect Trump takes the oath of office on January 20, the Constitution ordains that he “shall have Power to grant Reprieves and Pardons for Offences against the United States.” 

That has been taken to cover federal crimes, but not state ones — like the ones brought by the district attorney of Fulton County, Fani Willis. She charged Trump and 18 others with racketeering and other crimes against the Peach State in connection to efforts to reverse the result of the 2020 presidential election.

The prosecutions of Ms. Willis and of the district attorney of Manhattan, Alvin Bragg, have, alongside Trump’s victory in November, opened up hitherto unexplored constitutional terrain: Can a president be prosecuted for state crimes while in office? The answer to that question could determine the fate of Ms. Willis and Mr. Bragg’s cases — and the scope of the protections of the presidency. 

Pardons for state crimes usually reside within the purview of the highest executive authority in the state — the governor. Georgia is led by Governor Kemp, a prominent Republican who has had a fraught — to put it mildly — relationship with the 45th president, now the 47th president-elect.

Mr. Kemp opposed President Trump’s efforts in 2020 to overturn President Biden’s win in Georgia, and the president-elect backed his opponent two years later. He also called Mr. Kemp a “disloyal guy” and a “very average governor. … Little Brian, little Brian Kemp, bad guy.” The two let bygones be bygones this year, when Mr. Kemp endorsed Trump — and Georgia swung Republican.

Even if Mr. Kemp was moved to pardon Trump with respect to Ms. Willis’s prosecution, Georgia law ties his hands. The state is one of only six where pardons are granted by an independent board — the Georgia State Board of Pardons and Paroles. Unlike the presidential pardon power, where a conviction is not necessary, Georgia requires not only a “guilty” verdict or plea but also a five-year waiting period before a pardon can be issued.

If criminals want to bypass that half-decade waiting period, they must submit “substantial evidence” showing “that the sentence is either excessive, illegal, unconstitutional or void,” and that “such action would be in the best interests of society and the inmate.” The members of the Board of Pardons and Paroles are appointed by the governor but serve seven-year terms in an effort to insulate them from political pressure. 

Georgie tightened its pardon process after a report in Time Magazine in 1941 — “Georgia: Pardoner’s Tale” — that relayed how the then-governor’s “smart, ingratiating, gold-toothed” chauffeur was charged with going to “prison camps of Fulton County with pardons already signed and asked to see prisoners whom he did not know and who did not know him.”

There could be another path beside the pardon for Mr. Kemp to derail Ms. Willis’s possible pursuit of a sitting president. In March the governor signed a law that empowers a state commission to discipline and remove prosecutors. Before putting pen to paper he declared that the legislation “will help us ensure rogue and incompetent prosecutors are held accountable if they refuse to uphold the law.”

This is Mr. Kemp’s second attempt to establish such a body — an earlier version of the law required the approval of Georgia’s supreme court, which demurred on account of harboring “grave doubts” about the law’s constitutionality.

Ms. Willis, who like Trump won re-election last month, has decried the law, which could result in increased scrutiny of her office. She asserts: “This bill was never deemed necessary until an historic thing happened in 2020, and let’s just talk about it and tell the truth … in 2020, we went from having five district attorneys that are minorities to 14 that are minorities.”

The effort to convict Trump for election interference now falls solely to Ms. Willis, as Special Counsel Jack Smith, who spearheaded two federal cases against Trump, has already bowed to the insurmountability of prosecuting a sitting president. Both his Mar-a-Lago and January 6 prosecutions have been dismissed — albeit without prejudice, meaning they could be refiled during Trump’s post-presidency period. 

The Department of Justice’s Office of Legal Counsel reckons that there is a “categorical” prohibition on prosecuting a sitting president. Ms. Willis is under no such restriction, largely because the vulnerability of a sitting president to state prosecution has never arisen — until now. The Supreme Court’s ruling in Trump v. United States that all official presidential acts are presumptively immune would appear to apply to state as well as federal prosecutors. 

In Trump’s other state criminal case, at Manhattan, Mr. Bragg has asked Judge Juan Merchan to explore “various non-dismissal options” to freeze the 34 hush money convictions “in abeyance” for the pendency of Trump’s presidency. Trump wants the verdicts dismissed on account of his electoral victory and imminent swearing in as president for a second time. 

A similar debate could soon break out in Georgia, where Ms. Willis’s case has been on hold for months while first Judge Scott McAfee and now the Georgia Court of Appeals have heard arguments over whether Ms. Willis ought to be disqualified for accusing her defendants of “playing the race card” — and for conducting a secret romantic affair with her hand-picked special prosecutor, Nathan Wade. 

The court of appeals mysteriously canceled a hearing set for December 5 to hear oral arguments over whether what Judge McAfee called Ms. Willis’s “odor of mendacity” and “significant appearance of impropriety” are enough to dismiss her from the case. The appellate jurists could be weighing the impact of Trump’s electoral win — or could have determined that the already-completed briefing is sufficient to determine the question.