“I see it as a pragmatic move by Maduro to release pressure he was under that was disproportionately higher than the value of keeping him in jail,” Mr. Genser said. “Now is the time for sustained pressure on Maduro. Leopoldo’s transfer to house arrest confirms that the relentless pressure is working.”
Mr. López, a charismatic Harvard-educated politician who has been out of public view for more than three years, made a brief appearance on Saturday afternoon outside his house, where throngs of supporters gathered. He held up a Venezuelan flag, which he kissed at one point, but made no public remarks. Mr. Genser said Mr. López was prohibited from speaking publicly and giving interviews as part of the conditions of his release.
But in a statement released by his lawyer, Mr. López said: “I am not willing to give up my fight for the freedom of Venezuela. And if that means that I must return to a cell in Ramo Verde, I am willing to do so.”
“Tomorrow,” he added, “is the 100th day of our struggle in the street and that is where we will come together with the people. That is why we call on all the people of Venezuela to go out again throughout the country — strength and faith!”
Venezuela’s top court announced the news on Saturday morning in a couple of posts on Twitter, calling the release a “humanitarian gesture” and citing unspecified health problems of Mr. López’s. Later in the day, Vladimir Padrino López, Venezuela’s defense minister, said the release was evidence of the government’s commitment to “tolerance and dialogue.”
The case has been the subject of intense political and diplomatic negotiations since Mr. López, the founder of the political movement Voluntad Popular, or Public Will, was arrested in the wake of large street demonstrations in February 2014.
In September 2015, he was sentenced to more than 13 years in prison for inciting violent protests. Human rights advocates assailed the proceedings as unfair. Lacking firm evidence, prosecutors argued that Mr. López had used subliminal messages to stoke violence.
Mr. López’s wife, Lilian Tintori, has been a relentless advocate for her husband at home and abroad. She routinely posts videos to millions of followers on social media accounts documenting her unsuccessful attempts to visit her husband in the notorious Ramo Verde prison on the outskirts of Caracas, Venezuela’s capital. In February, Ms. Tintori met briefly with President Trump, who posted a photograph with her on his Twitter account and called for Mr. López’s immediate release.
Mr. López’s relatives and lawyers have called his treatment in prison cruel and appalling. They accuse prison staff members of keeping him in solitary confinement for long periods and of withholding food at times.
It was unclear what negotiations led to Mr. López’s release from prison. Javier Cremades, a Spanish lawyer who has been representing Mr. López, said on Twitter that Mr. López had made no concessions.
“Giving Leopoldo López house arrest shows how desperate and divided they are,” he wrote, calling the move “a sign of the weakness of a regime that is cornered.”
The transfer comes after months of daily protests against Mr. Maduro’s government that have left more than 90 people dead.