SAN FRANCISCO (CN) – Opponents of a Trump administration rule that makes most noncitizens arriving at the U.S.-Mexico border ineligible for asylum fired off a federal lawsuit Tuesday seeking immediate court action to block the new restrictions.

The new policy, enacted in an interim final rule by Attorney General William Barr Tuesday, renders all noncitizens that cross through a foreign country before reaching the southern border ineligible for asylum, with a few narrow exceptions.

“This is the Trump administration’s most extreme run at an asylum ban yet,” ACLU attorney Lee Gelernt said in a statement. “It clearly violates domestic and international law, and cannot stand.”

The ACLU represents four immigrant advocacy groups: East Bay Sanctuary Covenant, Al Otro Lado, Innovation Law Lab, and Central America Resource Center in Los Angeles. The same four groups sued last year to block a Trump administration rule that limited asylum eligibility to those who enter the country at official ports of entry. The Ninth Circuit upheld an injunction against that policy pending appeal in December last year.

Under new restrictions enacted Tuesday, those reaching the southern border can only seek asylum in the U.S. if they applied for refugee status in a transit country and were denied, or if they can show they are a victim of human trafficking.

“This rule will decrease forum shopping by economic migrants and those who seek to exploit our asylum system to obtain entry to the United States – while ensuring that no one is removed from the United States who is more likely than not to be tortured or persecuted on account of a protected ground,” Barr said in a statement announcing the new restrictions on Monday.

The rule also makes an exception for those who pass through countries that are not parties to the 1951 Convention on the Status of Refugees, the 1967 Protocol Relating to the Status of Refugees, or the Convention Against Torture. Because Mexico is party to those agreements and the only nation touching the U.S. southern border, it does not appear possible that someone arriving at the U.S.-Mexico border could qualify for that exception.

The plaintiffs say the new rule violates a clear congressional command in the Immigration and Nationality Act, which requires noncitizens be allowed to apply for asylum regardless of where they enter the U.S.

Under that law, the plaintiffs argue, noncitizens can only be denied asylum based on their relationship with a third country if they are firmly resettled in that country or subject to a safe third country agreement. The law also forbids categorically denying asylum “based on an asylum seeker’s route to the United States,” the immigrant advocates argue.

“The rule is a part of an unlawful effort to significantly undermine, if not virtually repeal, the U.S. asylum system at the southern border, and cruelly closes our doors to refugees fleeing persecution, forcing them to return to harm,” the plaintiffs state in their 34-page complaint.

The plaintiffs claim the law violates the Immigration and Nationality Act and Administrative Procedure Act. They seek a preliminary and permanent injunction against the asylum restrictions.

They are represented by Gelernt and Katrina Eiland of the ACLU Foundation Immigrants’ Rights Project.

A U.S. Justice Department spokeswoman declined to comment.