LOS ANGELES—The American Civil Liberties Union and other groups sued to halt a Trump administration rule that would bar most Central American immigrants from seeking asylum at the U.S. border.

“This is the Trump administration’s most extreme run at an asylum ban yet,” ACLU lawyer Lee Gelernt said Tuesday in a statement announcing the complaint filed in San Francisco federal court. “It clearly violates domestic and international law, and cannot stand.”

Under the new rule, asylum won’t be granted to anyone who hasn’t sought protection from persecution or torture from countries they travelled through to get to the U.S. The Justice Department and Homeland Security said the change was made because the asylum system is being abused. The government will now give priority to immigrants who have tried and failed to get asylum elsewhere and to victims of extreme forms of human trafficking.

“The large number of meritless asylum claims places an extraordinary strain on the nation’s immigration system, undermines many of the humanitarian purposes of asylum, has exacerbated the humanitarian crisis of human smuggling, and affects the United States’ ongoing diplomatic negotiations with foreign countries,” the departments said in a notice detailing the new regulation.

The lawsuit opens a new front in the sprawling legal fight by immigration groups against President Donald Trump’s efforts to stop the flow of Central American immigrants into the U.S. Earlier challenges led to courts ordering the government to end the separation of children from their parents and to halt the prolonged internment of minors.

The administration argues that the system is being overwhelmed at the southern border. There are 900,000 cases pending before immigration judges, almost half of which contain an asylum application, according to the government. The large majority of the asylum claims by immigrants at the Mexican border turn out to be meritless, the U.S. claims.

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