MANAGUA, NICARAGUA, JAN. 31 -- By lifting a six-year state of emergency in conformity with the Central American peace plan, the Sandinista government accepted some key restrictions on its legal powers, Nicaraguan jurists say. But opposition leaders remain wary that the revived rights will be respected, or, if so, sustained.

Ending of the state of emergency was viewed by top Sandinistas and other regional leaders as one of Managua's most important concessions in a five-month peace process, through which Nicaragua hoped to persuade the U.S. Congress to stop supporting the rebels, known as contras.

If the government upholds the constitutional liberties it restored, the opposition should be able to carry out its activities with little fear of persecution -- a result Costa Rican President Oscar Arias, author of the regional peace accord, hoped to achieve.

But 12 days after President Daniel Ortega ended the emergency, the results are mixed. The government lifted suspension of eight news radio programs and four opposition publications, legalized several labor union locals, allowed at least two strikes and freed a number of political prisoners.

But it also denied permits for some opposition demonstrations and dispatched militant Sandinista party followers to harass and disrupt others.

Sandinista leaders have threatened, and opposition leaders expect, that the new rights will be curtailed at some point if the U.S. Congress approves a $36 million package of contra aid in votes due Tuesday and Wednesday.

In interviews published in recent days in Sandinista newspapers, Nicaraguan legal experts, including Supreme Court Chief Justice Alejandro Serrano, outlined due-process rights that they said are the main ones now back in effect.

The much feared state security police can no longer hold prisoners incommunicado, the jurists say. Prisoners have right to counsel and must appear in court within 72 hours to be charged or must be freed. Written warrants are required to make arrests.

In recent years the state security system, run by Interior Minister Tomas Borge, sometimes detained more than 1,000 Nicaraguans it accused of collaborating with the contras, placing them in hidden holding cells around the country for months without charging or trying them. However, a top government official said that only about 90 people are still in those cells, and most of them now could be freed immediately through legal action.

Also revived are the rights to strike, travel freely in and out of the country and hold public demonstrations. The laws now even provide for punishment of officials who disregard such rights.

At a press conference last week, Borge pledged to abide by the 72-hour limit on detentions, adding, "It will undoubtedly affect the quality of our investigations, since we don't practice any torture or beatings against our prisoners. The Nicaraguan constitution is one of the world's most restrictive of the powers of the security agencies."

Borge promised that all opposition requests for demonstration permits would be granted.

But after years of being hounded, arrested, infiltrated and spied on, many opposition party leaders are still smarting. They say their lives will not improve under the new terms. Some predict new forms of harassment. Others are reluctant to test the new freedoms.

"We've gone from a state of emergency to a state of terror. The Sandinistas' approach is to dig in with their fingernails while they wear smiles on their faces," charged Agustin Jarquin, a top member of the centrist Social Christian Party. Two days after the emergency was lifted, a gang of pistol-brandishing Sandinistas staged a nighttime demonstration in front of his party's headquarters, where some fistfights resulted.

In an interview, Carlos Fernando Chamorro, editor of the Sandinista party newspaper Barricada, said such actions are "a message that is meant to be heard" to remind the opposition parties there are limits to the new liberties.

Chamorro noted Sandinista party followers have received somewhat contradictory guidelines from their leaders on how to respond to the opposition's new leeway. They have been instructed not to be "provoked" by the opposition, but also "not to be defeated in the battle for the streets," Chamorro said.

"There's no state of emergency anymore, but many mechanisms that restrain opposition actions are still in place," said Virgilio Godoy, president of the Independent Liberal Party, another middle-of-the-road group.

Godoy said his party called a rally last Sunday in Masaya, 20 miles south of Managua, a stronghold of anti-Sandinista feeling. Sandinista police first granted a permit, Godoy said, then revoked it, then granted it again late on the eve of the event, confusing the party's preparations and reducing attendance.

Today, however, when the opposition coalition known as the Democratic Coordinating Group staged its first march since an indoor ceremony was disrupted by rock-throwing Sandinistas Jan. 22, the Sandinista police granted a permit without delay and accompanied the uneventful protest to prevent traffic jams.

The police stood by quietly while sprayers painted antigovernment slogans across the front of a ruling party block headquarters and a policeman's booth. Only about 500 opposition members turned out.

Godoy said 283 Liberal Independent Party members remain in jail on political charges. But he dismissed with a weary shake of his head the notion of hiring lawyers to petition for their release under the laws now in effect. He predicted the government will continue to ignore habeas corpus procedures, in any case.

By contrast, Jarquin's Social Christians immediately put a lawyer to work on the cases of 20 party members picked up by police Jan. 10 in the northern city of Esteli, allegedly on suspicion they were draft dodgers. As a result, three were freed last week.

Meanwhile, the opposition Labor Unification Central, a union federation, was authorized Thursday to resume publishing its newspaper, Solidarity, after a two-year shutdown. Of 26 locals for which the union has been seeking legal recognition for years, two had it granted.

The federation held a one-day strike for higher pay at a state-owned cement factory in Managua, its first in years. The managers immediately agreed to negotiate on wages.

"We can't lie about this. Maybe the government is only doing it for publicity before the vote in Washington, but it's good for us," said the federation's political secretary, Jose Espinoza.

International human rights groups welcomed Ortega's abolition of the Popular Anti-Somocista Tribunals, where defendants accused of collaborating with the contras faced highly informal and unorthodox trials. But no one is sure whether the 716 cases transferred to regular courts will fare better there.

Justice Minister Rodrigo Reyes admitted that the court system suffered neglect in recent years, "when the principal problem was the war against the contras." Dockets are backed up and there are few skilled judges.

The impartiality of the court system was thrown in doubt last December when three Supreme Court justices resigned to protest the government's repeated failure to obey its rulings. Ortega appointed a new seven-man court, which opposition deputies in the National Assembly refused to ratify, asserting it was pro-Sandinista.

Reyes pointed out that several restrictive decrees outlawing a broad range of supposed pro-contra activities remain in effect.

"In its search for peace, the government lifted the emergency when the {U.S.-funded contras' war} isn't over yet. We've given everything and so far we haven't gotten anything in return," Reyes complained.

But the Labor Unification Central's secretary general, Alvin Guthrie, expressed a fresh if guarded optimism. "The Sandinistas still have a chance if really they open things up. The people are tired of war. They want a change," Guthrie said.