The US attorney general has ruled that victims of domestic abuse and gang violence should no longer generally qualify for asylum in the US.
Jeff Sessions' ruling overturns a 2016 decision which granted asylum to a woman from El Salvador who had been raped and abused by her husband.
Activists criticised the move, saying it will affect tens of thousands.
Mr Sessions has said he has a "zero tolerance" stance toward illegal immigration on the country's border.
"Generally, claims by aliens pertaining to domestic violence or gang violence perpetrated by non-governmental actors will not qualify for asylum," Mr Sessions wrote in his 31-page ruling released on Monday.
"The mere fact that a country may have problems effectively policing certain crimes - such as domestic violence or gang violence - or that certain populations are more likely to be victims of crime, cannot itself establish an asylum claim."
How did the ruling come about?
The unnamed woman - known in court documents as A-B - entered the US illegally in 2014, and requested asylum on the basis her former spouse had repeatedly abused her "emotionally, physically and sexually".
US and international law currently say that people can seek asylum if they fear persecution at home on the basis of their race, political opinion, nationality, religion or because they belong to a particular social group.
The US Board of Immigration Appeals found in 2016 that the woman qualified under the "particular social group" definition, but Mr Sessions overturned the finding on Monday.
He wrote in his ruling that the category was currently "inherently ambiguous" and concluded it should not be used as "'some omnibus catch-all' for solving every 'heart-rending situation"'.
"The asylum statute does not provide redress for all misfortune," he said, adding that the woman was a victim of "private criminal activity" rather than state-sponsored persecution.
"Asylum was never meant to alleviate all problems, even all serious problems, that people face every day all over the world," the attorney general said in advance of his ruling.
What happens next?
It is unclear how many cases are affected by the ruling, but activists say that at least 10,000 people per year are granted asylum in the US on the basis of domestic abuse and gang violence in their home countries.
Pro-immigration groups say they plan to fight Mr Sessions' decision, which is part of a larger effort by the Trump administration to place restrictions on immigration.
Last week, Mr Sessions defended the department's policy of separating migrant children from their parents after they have crossed into the US.
Activists say the ruling will especially resonate in Central America, where gang violence is rampant.
Migrants from that region frequently cite gang violence as the reason for seeking refuge in the US.
Latin American countries also have some of the worst rates of violence against women in the world, according to the UN.
What has the reaction been?
The decision "will no doubt result in sending countless mothers and children back to their abusers and criminal gangs," said Beth Werlin of the American Immigration Council.
"Turning our backs on victims of violence and deporting them to grave danger should not be the legacy sought by any administration."
Frank Sharry, founder of America's Voice, an immigration reform group, tweeted: "Sessions is locking Central Americans inside the burning house they're trying to escape."
The inhumanity of the Trump Administration’s asylum policy is staggering. They continue to separate children from their families, and now they're targeting victims of domestic violence. This change will put the lives of particularly vulnerable people at risk. https://t.co/IoDmHAT1w1— Senator Bob Casey (@SenBobCasey) June 11, 2018
Democrat politicians hit out at Mr Sessions' ruling. The senator for Connecticut, Richard Blumenthal, labelled it "shameful".
"America is better than this, but apparently Attorney General Jeff Sessions is not," he said on Monday.
"Today's decision will send untold numbers of refugees to their deaths. Attorney General Sessions: their blood is on your hands."