BUENOS AIRES -- In the developing democracies of South America, newspapers and broadcast stations have recovered freedoms outlawed or restrained during years of military rule.

But defining new roles for the media that are appropriate for the region's struggling systems is testing the experience of editors and the patience of politicians.

In Peru, for instance, news organizations have come under repeated pressure to play down reports of leftist guerrilla violence. In Ecuador, a strong-willed civilian president has sanctioned the most critical independent publications.

Perhaps the continent's most pronounced debate over management of the news is under way here in Buenos Aires, which boasts an abundant press including 10 daily newspapers.

Political tensions over military issues are pushing reporters to assert their rights, oppose outside constraints and challenge the government's continued deep involvement in broadcast journalism.

The latest dispute centers on who has the right to coverage in the media. The question first arose in April when Army officers rebelled to protest trials of military and police personnel for human rights violations.

Some radio stations and news services carried interviews with Aldo Rico, the lieutenant colonel who commanded the uprising at the Campo de Mayo base near Buenos Aires. Government officials accused the news organizations of serving as mouthpieces for the mutineers and aggravating the crisis.

More recently, right-wing forces sought to buy space in five newspapers. They wanted to publish an advertisement signed by 4,800 people proclaiming "recognition {of} and solidarity" with one of Argentina's most notorious former junta members, Gen. Jorge Rafael Videla. The cashiered general is serving a life prison sentence for masterminding the antiguerrilla campaign of the 1970s.

Tipped off by typesetters who saw the advertisement before it was scheduled to appear, press-operators' unions and some journalists filed a joint lawsuit to block newspapers from printing what they claimed was a right-wing provocation.

Calling the advertisement a "eulogy of crime," they cited a law that prohibits statements in support of criminal activity. A judge subsequently banned the advertisement. Outraged by this abridgment of press freedom, several dailies have appealed the ruling.

In casual conversations around the city, it is not uncommon to hear some Argentines argue forcefully in favor of opening the media to all voices, while others, bitter about the military period, adamantly oppose letting former dictators and their sympathizers take advantage of the country's restored press liberty.

As news organizations battle to keep the courts from exercising prior censorship, they are also trying to prevent Congress from forcing things into print or onto the air. Legislators have proposed a "right to reply" bill that would require news organizations to print or broadcast the responses of "anyone affected directly or indirectly by information or opinions expressed in any communications medium."

Newspaper publishers have criticized the bill, and an editorial in the Buenos Aires Herald warned that the measure "tends toward authoritarian designs that would be detrimental to freedom of expression rather than promoting it."

The government itself, while opposed to outside censorship of the media, would prefer to see journalists exercise a measure of self-censorship until democracy is more consolidated.

President Raul Alfonsin has on occasion lost his temper over press coverage. He lashed out last February at Clarin, a major daily, saying it "specializes in headlining stories in a definite way, as if it wanted to make the Argentine people lose faith and hope."

Most local newspapers are privately owned, but the broadcast field is still dominated by government stations, a legacy of more than four decades of authoritarian rule. The government has not been shy about using this broadcast power for propaganda purposes.

During the Army rebellions, for instance, state networks repeatedly urged people to go to downtown plazas around the country and demonstrate support for democracy. The phrase "Dictatorship or Democracy" flashed across television screens as a rallying cry.

"The government will eventually turn over the stations to private owners," predicted a prominent local columnist, "but it will probably do so on the last day it is in power, and then only to friends."

Some journalists see more than a little hypocrisy in current pleas by some leading papers for freedom of expression after the silence they kept during military rule.

"Had the issue been tackled with the same amount of passion a few years ago," Monica Gutierrez wrote this month in the daily La Razon, "not only would it have preserved the constitutional guarantee but also a number of Argentine lives."