In this Sept. 22, 2011 file photo, a youth jumps from an overpass into a river in Paragominas, northern state of Para, Brazil. A judge has halted a planned mining development in the ecologically sensitive and protected area. Andre Penner/Associated Press
This Sept. 15, 2009 file photo shows a deforested area near Novo Progresso in Brazil’s northern state of Para.

 A federal judge in Brazil has temporarily halted a plan by President Michel Temer to allow mining in a large area of the Amazon forest, dealing a victory to environmental activists who denounced the initiative as potentially calamitous.

In a ruling issued Tuesday, Judge Rolando Valcir Spanholo said the executive branch had exceeded its authority in rescinding the designation of a 28,500-square-kilometre region known by the Portuguese acronym RENCA as a protected area through a presidential decree. The judge said only Congress could make that change.

The ruling came after the government sought to respond to an international outcry by issuing an updated version of the RENCA decree that more broadly outlined steps to mitigate environmental damage, safeguard the rights of indigenous communities and retain protected areas. But opponents say that the plan will hasten development that has encroached on the rain forests and accelerate deforestation and the displacement of native peoples.

The injunction was granted in response to a lawsuit filed by Antonio Carlos Fernandes, a lawyer and university professor in the northeastern city of Fortaleza who said he felt compelled to act after reading about the growing opposition to the decree, both in Brazil and abroad.

“I’m a regular citizen,” he said in an interview. “And now I have certainty that a regular citizen can have a lot of strength.”

The government has argued that authorizing regulated mining in the region would curb illegal gold mining and generate new jobs. The area also contains deposits of iron and copper. The government has said it will appeal the decision.

While the appeal process plays out, regional prosecutors and members of Congress who oppose opening the area to mining are gearing up for a protracted legal and legislative struggle.

“The suspension of President Temer’s unilateral decree with its severe threats to vast Amazonian forest offers a welcome and temporary reprieve,” said Christian Poirier, the program director for Amazon Watch. “Today’s ruling upholds constitutional guarantees and puts the brakes on this drastic regression, but is ultimately vulnerable to being overruled by higher courts.”

Some Brazilian celebrities have recently inserted themselves into this and other environmental disputes. “SHAME!” the model Gisele Bundchen, who appears to have swayed Temer on a previous environmental controversy, wrote in a post in Portugese on Twitter. “We’re auctioning off our Amazon.”

In June, after a plea from Bundchen on Twitter, Temer vetoed legislation that would have decreased the size of a national forest area in the Amazon. In an uncharacteristic gesture, the president responded on Twitter, announcing his veto. Last week, the issuance of the RENCA executive order opening up an area the size of Denmark to mining operations drew criticism from Bundchen and other celebrities.

The future of RENCA has become the latest dispute in the fight between Temer and conservationists, who say the president has become beholden to powerful political factions that represent the interests of the agricultural, ranching and mining industries.

Earlier this summer, Temer, a deeply unpopular leader, avoided standing trial on corruption charges after a majority of members of the House of Representatives voted to spare him. Those votes were widely reported to have entailed horse trading.

Temer, who came to power last year after the impeachment of President Dilma Rousseff, has pared back environmental protections and slashed the budgets of agencies that enforce environmental laws and combat illegal deforestation. His government has also cut the budget of the agency tasked with protecting the rights of indigenous communities. Temer’s decree earlier this month drew a barrage of criticism from lawmakers and activists, including moves to file lawsuits and block the decree in Congress, as it would allow mining in an area of roughly 17,800 square miles (46,000 square kilometers) that has been protected since 1984.