The Supreme Court cleared the cancer-stricken president to indefinitely postpone his re-inauguration and said his existing administration could remain in office until he is well enough to take the oath.
The court re-iterated that Chavez could swear in again "on a later occasion before the Supreme Court."
It was the last legal hurdle to a government plan for resolving the vacuum created by Chavez's illness that met fierce resistance from the opposition, which had argued it was unconstitutional.
Henrique Capriles, who ran unsuccessfully against Chavez in the October presidential elections, accepted the unanimous ruling as "binding" but said it did not end the uncertainties facing the country.
"Now the ruling has been handed down. There is an interpretation by the Supreme Court," Capriles said before shifting his aim to Maduro, Chavez's handpicked successor.
"The excuses are over, Mr Maduro. Now it falls to you to assume the responsibility of the office and to govern."
But even without the official ceremony, and despite the lingering controversy, Venezuela's government prepared for a day of celebration of Chavez, who won re-election in October by a healthy margin, despite his health battles.
"We're going to have a grand event in homage of President Chavez. We are all going to swear in everyone with this constitution," said Vice President Nicolas Maduro had said on Wednesday, inviting all Venezuelans to turn out in support of the absent president.
"It is a historic day, because it is the start of President Chavez's 2013-19 mandate," Maduro said while meeting with the Cabinet.
Leaders of other leftist Latin American government had already begun arriving in Caracas to pay tribute to Chavez, 58, who has not be seen in public since he underwent cancer surgery a month ago in Havana.
The military announced it was reinforcing security in the city and at other strategic points to ensure the day was observed peacefully.
And the government stopped a broadcaster, Globovision, from airing videos about the controversy over Chavez's non-inauguration, saying they risked inciting political "intolerance."
Globovision, known for being critical of the government, denounced the ban as an act of censorship.
Chavez, who is recovering from a fourth round of cancer surgery in Havana, will be marking a full month since he has been seen in public, the longest stretch of his 14 years in power.
The government has said that he is recovering from complications from surgery, most recently a severe pulmonary infection that had resulted in a "respiratory insufficiency."
Information Minister Ernesto Villegas said late Monday that Chavez's medical condition was unchanged.
The top court's seven magistrates -- all appointed by the Chavez-controlled National Assembly -- unanimously ruled on Wednesday that it was constitutional to delay the swearing in.
It said the officials of the current administration "will continue fully exercising their functions under the principle of administrative continuity."
Supreme Court president Luisa Estella Morales, who read out the decision, also ruled out convening a medical board to assess the health of the president.
Maduro welcomed the court ruling as "a sentence for peace, for justice, for stability." He also highlighted the expressions of support he had received from other leaders, including Brazilian President Dilma Rousseff.
Uruguay's President Jose Mujica was the first foreign president to arrive here for Thursday's show of support.
"We have to offer all possible support for a way out at a moment of tension that is the least disruptive for the future of the Venezuelan people," Mujica told Uruguay's public television.
"From the point of view of the popular decision, I don't think there are any doubts. And for that reason, it seems to me they have to find an institutional way out," said Mujica.
Bolivian President Evo Morales, Nicaraguan President Daniel Ortega, Haitian Prime Minister Laurent Lamothe, and Foreign Ministers Hector Timerman of Argentina and Ricardo Patino of Ecuador also have confirmed their attendance.
In Ecuador, President Rafael Correa said the Venezuelan leader's absence would be a "blow" for Latin America.
Capriles, who had urged Latin leaders not to attend what was a political event, said he was pleased that most presidents from the region were not coming.
Throughout his illness, first detected in June 2011, Chavez has refused to relinquish the powers of the presidency, even when leaving for Cuba for his latest surgery.
The charter says new elections must be held within 30 days if the president-elect or president dies or is permanently incapacitated either before he takes office or in the first four years of his six-year term.