In a decision immigrant rights advocates said could have horrific consequences for thousands of people fleeing violence in Central America, Attorney General William Barr ruled Monday that being an immediate member of a persecuted family is not sufficient grounds to seek asylum in the United States.

According to immigration experts, Barr’s move rewrites years of law and represents the Trump administration’s latest far-reaching assault on asylum protections.

“This is a continuation of an attack on Central American asylum seekers,” Lee Gelernt, deputy director of the American Civil Liberties Union’s Immigrants’ Rights Project, said in a statement. “In Central America, gangs will attack one family member but threaten another family member.”

As the New York Times reported,

Migrants are eligible for asylum in the United States if they can prove they were persecuted because of their race, religion, nationality, or what immigration laws describe as “membership in a particular social group or political opinion.” Mr. Barr’s ruling concluded that the immigration appeals court ‘erred’ in finding that a migrant’s family qualified as a persecuted social group.

Federal law allows the attorney general to overrule the decisions of the immigration appeals board, which is part of the Justice Department. But like many of the Trump administration’s recent attempts to restrict migration to the United States’ southwest border, Mr. Barr’s ruling was expected to be challenged in the wider court system, immigration advocates and lawyers said.

“In this latest assault on asylum, the administration has taken the absurd position that families are not recognized within societies as distinct groups,” Anna Gallagher, executive director of the Catholic Legal Immigration Network, said in a statement. “This is shameful.”

Observers pointed out that Barr’s decision appeared to leave an exception for members of wealthy or politically connected families.