Nicolas Sarkozy served about three weeks of a five-year prison sentence for his conviction in a campaign finance scandal.

Former President Nicolas Sarkozy of France was granted conditional release from prison on Monday, less than a month into a five-year sentence for his conviction in a campaign finance scandal.

Mr. Sarkozy, who has denounced the conviction, was the first former head of state to be jailed in more than a half-century in France. His case set off fierce debates in the country about fairness and judicial independence.

He was convicted in September of conspiring to seek funding for his 2007 presidential campaign from the government of Col. Muammar el-Qaddafi, the Libyan former strongman. Once Mr. Sarkozy began serving his sentence on Oct. 21 at a prison in southern Paris, his lawyers submitted a request for an early release, pending an appeal of the conviction.

On Monday, the Paris Court of Appeal agreed to grant Mr. Sarkozy that early release — which was largely expected — and place him under judicial supervision, meaning restrictions.

Christophe Ingrain, one of Mr. Sarkozy’s lawyers, welcomed the decision but called it a first step.

“The next step is the appeal trial, and our job now, Nicolas Sarkozy’s and ours, is to prepare for this appeal trial,” he told reporters outside the courtroom.

Hours after telling the court by video link from prison that his incarceration had been “grueling” and “a nightmare,” Mr. Sarkozy was photographed arriving back at his home in Paris.

“My energy is focused solely on the single goal of proving my innocence,” he later wrote in a post on X that also thanked his supporters.

By filing an appeal, Mr. Sarkozy is now again presumed innocent. And it is not uncommon for French courts to allow those who appeal their conviction to remain free, especially nonviolent offenders.

Under the terms of his release, Mr. Sarkozy will be barred from traveling abroad and from contacting people involved in the case or French justice officials, according to the court.

It specifically mentioned France’s justice minister, Gérald Darmanin, as one of the people Mr. Sarkozy is forbidden to contact while under judicial supervision.

A recent visit by the justice minister to Mr. Sarkozy in prison had raised some eyebrows in France. Some judges and lawyers said it contradicted the impartiality that Mr. Darmanin should embody as justice minister.

Mr. Darmanin has defended his decision to visit Mr. Sarkozy, telling reporters that it was his prerogative because the country’s prison administration fell under his portfolio as justice minister.

“I imagine that if I didn’t do my job as minister and something happened to President Sarkozy in prison,” he said, “it would be perfectly natural for Parliament, and perhaps other bodies, to hold the minister accountable. So, I did my job.”

Mr. Sarkozy, a pugnacious conservative politician, was the president of France from 2007 to 2012. He has retained political influence since leaving office despite his high-profile legal battles, which have included trials about corruption, influence peddling and campaign spending violations.

This latest case ignited a partisan debate between those on the French right, who deemed his incarceration unfair, and those on the left, who said that Mr. Sarkozy should be treated like any other convict.

It also put the French prison administration under immense pressure to maintain Mr. Sarkozy’s security without giving the impression that he was receiving special treatment.

Mr. Sarkozy spent his incarceration in solitary confinement, as is customary to ensure the security of notorious inmates. He lived in a roughly 100-square-foot cell with a bed, a desk, a bathroom and a landline telephone, according to the prison’s administration. He also had access to a library and a gym and was allowed at least three family visits per week.

Representatives of prison labor unions said Mr. Sarkozy had been treated better than most inmates in France, who often share cells of a similar size with other people and are granted fewer family visits.

One episode was reported during Mr. Sarkozy’s time at La Santé. The Paris public prosecutor said it had investigated reports of a video posted online and seemingly filmed by an inmate in which threats against Mr. Sarkozy could be heard.

As part of that investigation, two inmates will appear before a court on Dec. 19, according to the prosecutor — one accused of uttering death threats against Mr. Sarkozy and the other of complicity in that.