By ALEXEI BARRIONUEVO

VILA DOS CRENTES, Brazil - Raimundo Teixeira de Souza came to this sweltering Amazon outpost 15 years ago, looking for land. He bought 8 hectares, he said, but more powerful farmers, who roam this Wild West territory with rifles strapped to their backs, forced him to sell much of it for a pittance.

Then someone shot and killed Mr. de Souza’s 23-year-old stepson in the middle of a village road two years ago, residents said. No one has been arrested. In fact, the new police chief has no record that the crime was even investigated by his predecessor. It is hardly surprising, the chief said, considering that he has only four investigators to cover an area of rampant land-grabbing and deforestation the size of Austria.

“We are being massacred,” said Mr. de Souza, 44, who leads the local residents’ association. “We just want to work and raise our children.”

It has been this way for decades, residents say. Throughout this huge stretch of the Amazon, the state has been virtually nonexistent, whether in the form of police officers or clear records of land ownership, giving way to a brazen culture of illegal land seizures, often at the tip of a gun barrel.

But using a new law, Brazil’s government is trying to impose order on this often lawless territory, and in the process, possibly nip away at a broader global concern: deforestation and the threat of climate change that comes with it.

For the first time, the Brazilian government is formally establishing who owns tens of millions of acres across the Amazon, enabling it to track who is responsible for clearing forests for logging and cattle - and who should be held accountable when it is done illegally.

“The government will finally know whose land it is, and who is responsible for what goes on there,” said Thomas E. Lovejoy, the biodiversity chair for the Heinz Center for Science, Economics and the Environment in Washington.

This county in the state of Para is the worst place for forest destruction in Brazil, and environmentalists say they hope that the new law, approved by Brazil’s Congress in June, will help the government finally enforce its official limits on clearing land.

But it is a huge and messy undertaking. Clear ownership records exist for less than 4 percent of the land in private hands throughout the Brazilian Amazon, government officials said. Here in Para, officials have discovered false titles for about 130 million hectares, almost double the amount of land that actually exists, according to federal officials.

And while small farmers like Mr. de Souza are pinning their hopes on the law, many larger-scale land holders say they have sacrificed too much blood and sweat for bureaucrats in Brasilia, the capital, to force new rules upon them.

“Everything we have today was built from our own desire to work,” said Jorgiano Alves de Oliveira, 68, who raises cattle and grows cocoa.

The problem began with the military dictatorship in the 1960s and 1970s, which invited settlers to occupy the Amazon but required them to clear forests to gain access to land and credit.

Growing criticism of Brazil’s Amazon policies pushed the civilian government of the 1980s to develop laws that, on paper at least, were among the world’s most protective of forests. But with scant presence of authorities to enforce them, the laws did little to stop the widespread grabbing of land.

“This chaos of legal insecurity was the most important basis for the perverse incentives in the Amazon to pillage rather than to preserve or to develop, and constant incitement to violence,” said Roberto Mangabeira Unger, the former minister for strategic affairs who helped develop the new land law.

Since the days of the dictatorship, this huge county in Para State, known as Sao Felix do Xingu, has drawn hardy settlers and prospectors in search of cheap land, good soil, a rich array of minerals and rare Amazon fruits.

But notorious criminals have also found refuge. Leonardo Dias Mendonca ran a vast criminal enterprise from Sao Felix, which included a fleet of planes used to deliver weapons to Colombian rebels in exchange for drugs, before being convicted in 2003.

Disputes in Sao Felix were traditionally settled with violence, said Waldemir de Oliveira, the leader of the Sao Felix agricultural association. “It was the law of the strongest,” he said. He and other residents say the violence is diminishing but is still a major worry.

At the closest police station, more than 160 kilometers away, Chief Alvaro Ikeda said killing was common and witnesses often are too afraid to come forward. “I cannot guarantee the witnesses’ life,” he said. “I cannot even guarantee my own life.”

Ranchers like Orquizio Moreira were attracted by cheap land to the Amazon region, where lawlessness prevails. / ANDRÉ VIEIRA FOR THE NEW YORK TIMES