A freedom of information law has taken effect in Brazil, challenging an embedded culture of secrecy and bureaucracy.

Proponents, including President Dilma Rousseff, said the measure is nothing short of a revolution for a system that has kept tight control over information for decades.

But even as the president hailed the potential of the law that went into effect Wednesday, experts cautioned that it will take more than a piece of paper and political goodwill at the top to change attitudes about the flow of information. Most citizens, even journalists, are unfamiliar with the concept of free access to public information.

Experts say a lack of transparency has allowed corruption, inefficiency and wastefulness to go unchecked in the public realm. Last year, five of Rousseff's ministers were sacked or stepped down following public allegations of corruption and misuse of public money.

"From now on, transparency is obligatory, under law, and will function as an efficient inhibitor of all the bad uses of public money, and of violations of human rights," Rousseff said on Wednesday, a day that also marked the inauguration of a truth commission that will investigate human rights abuses committed during the military dictatorship from 1964 to 1985.

The president, who as a leftist guerrilla was imprisoned and tortured in the early 1970s under a military regime, acknowledged that both developments are the result of decades of work toward democratic ideals.

Brazil's 1988 constitution enshrined the right to access information, but the new measure gives citizens a legal tool to enforce that right in a court. Its scope is broad: Unlike the U.S. Freedom of Information Act, which applies to the executive branch at the federal level, Brazil's law covers all branches of government at all levels. However, there is still no set of regulations detailing how citizens can ask for data, and what municipal, state or federal officials must do to comply.

The sweep of the measure poses a significant challenge to the country, said Brazil-based researcher Greg Michener, who specializes in transparency and freedom of information laws. If civilians and the media demand compliance, the law could be a real force for positive change, he said. But Brazilians might also just throw up their hands at the enormity of the job, and abandon the idea. This is a country where some laws simply "don't take," he said, and there is a danger this one could fall by the wayside if Brazilians don't push for compliance.

"These laws are sophisticated instruments, and depend on an informed populace," he said. "You'd think the media would be most interested, that they'd want better information. But there isn't really an awareness of what the law is in the Brazilian press."

Michener compared Brazil to Mexico, which passed its own information access law in 2002. It was implemented a year later at the federal level, but it took five years to include it in the constitution, extending it to other levels and branches of government, where it is still being implemented. Mexico also created an autonomous institution to govern the law's application. The Brazilian law allowed six months for preparation, and will be overseen by an existing government oversight body which also has other responsibilities, said Michener.

Groups that pushed for the bill say they are trying to ensure it doesn't end up on the dustbin of well-intentioned laws that never took hold. The nonprofit watchdog group Contas Abertas, "Open Accounts," celebrated the law's enactment by shooting out 100 requests for information all over the country, to all branches of government. Brazil's federal comptroller's office said there were just over 700 requests in total on the law's first day.

"It was a fight for us to get to this point," said Gil Castello Branco, founder of Contas Abertas. "But I always remember what Thomas Jefferson said, that the execution of the law is more important than the making of them. This is particularly true in Brazil, where some laws are never followed."