On Monday, the Trump administration made likely its most brazen attempt yet to block the asylum claims of people fleeing violence in Central America. A new rule published in the Federal Register, which will take effect on Tuesday, would bar people from eligibility for asylum if they pass through a third country on their way from their home country to the United States and do not first apply for asylum there.

For example, if victims of violence or persecution in Honduras claim asylum in the United States after first traveling through Guatemala and Mexico, they can be denied on the basis that they did not first claim asylum in either of those countries. This would apply to the vast majority of asylum-seekers arriving at the U.S.-Mexico border. The rule does not include an exception for unaccompanied children.

Acting Homeland Security Secretary Kevin McAleenan said in a statement that the move “will help reduce a major ‘pull’ factor driving irregular migration to the United States … leading to fewer individuals transiting through Mexico on a dangerous journey.” Civil rights groups including the ACLU are already planning to challenge the rule in court, and they’ll probably have a pretty good case.

The rule appears to contradict the intent of Congress, which established a broad eligibility for seeking asylum in the 1980 Refugee Act, in accordance with U.S. obligations under international law. American law does allow the U.S. to remove asylum-seekers to a safe third country if the two have a bilateral or multilateral agreement to that effect. The U.S. has such an agreement with Canada: Migrants have to apply for asylum in the first of those two countries they reach.

The Trump administration has been pushing to reach a Canada-style “safe third country” agreement with Mexico and Guatemala in recent weeks, with little success. In June, when the U.S. and Mexican governments negotiated an understanding to forestall Trump’s threat to impose tariffs on Mexican goods, the two sides publicly contradicted each other on whether this included such an agreement. Mexico’s foreign minister later rejected the idea.

While Mexican President Andrés Manuel López Obrador’s government has accommodated and cooperated with the Trump administration’s zero-tolerance immigration policies to a surprising extent, “safe third country” is a line it hasn’t been willing to cross. Mexico does not have the capacity to process the massive number of Central American migrants and can hardly be considered safe for them either. Next month marks the ninth anniversary of the massacre of 72 Central American migrants by criminal gangs of northeastern Mexico. Widespread crimes against migrants continue with a depressing degree of impunity today, even as the Trump administration has enacted a new policy—the lawfulness of which is being challenged in federal court—forcing some asylum-seekers to wait in Mexico while their asylum cases go through the immigration system, a process that often takes years.

Plagued by gang violence and political corruption, Guatemala, a country that is a major source of U.S. asylum-seekers, is even less prepared than Mexico to act as a refuge for those fleeing from other countries. Nonetheless, there were reports last week that the Trump administration was due to sign an agreement to designate Guatemala a safe third country. According to some reports, this would have been a radically expansive deal that would allow the U.S. to send any asylum-seekers, not just Central Americans who had passed through the country, to Guatemala.

The rule is vulnerable to legal challenge and may not even accomplish what it’s set up to do.

Guatemalan President Jimmy Morales was due in Washington on Monday to discuss a potential agreement, but the meeting was called off because Guatemala’s constitutional court has not yet ruled on several legal challenges meant to prevent Morales from agreeing to Trump’s request.

In the absence of a negotiated safe third country deal, the administration seems to have simply acted unilaterally and declared that the obligation is on refugees to apply for asylum in any country they cross on their way to the U.S., safe or not. (The rule change does carve out an exception for countries that are not party to the Refugee Convention or the Convention Against Torture, though that does not apply to the vast majority of Western countries.)

Crucially, the rule change also notes that “aliens who fail to apply for protection in a third country of transit may continue to apply for withholding of removal under the Immigration and Nationality Act” or under U.S. obligations as a party to the Convention Against Torture.

What this means is that “[i]f the threats you face back home amount to a likelihood that you would be tortured, then you can apply to stay in the United States,” explains Susan Gzesh, an immigration law specialist and the executive director of the Pozen Family Center for Human Rights at the University of Chicago.

“Withholding of removal” is not the same thing as asylum, though. It entails no pathway to eventual U.S. citizenship and does not allow your dependents to get it with you. But its inclusion in the rule change suggests that those who fear torture in their home can still claim the right to remain in the U.S.—and fight their deportations in court—even if they are denied asylum under the new rule.

So, the rule is vulnerable to legal challenge and may not even accomplish what it’s set up to do. But it can be seen as yet another attempt by the administration to shirk America’s obligations to refugees under U.S. and international law, as well as an attack on the norms underlying those laws. From a foreign policy perspective, it will further antagonize regional allies in the service of Trump’s domestic political agenda.

It won’t be the last time.