Those who cross the border illegally will be unable to claim asylum after President Trump signed a proclamation limiting such claims on Friday. The measure is intended to circumvent laws that allow migrants to apply for asylum independent of how they arrive to the United States.

“We need people in our country, but they have to come in legally and they have to have merit,” Mr. Trump said Friday as he departed for Paris, according to the Associated Press.

Through the proclamation, Mr. Trump is exercising powers he previously tapped to implement the travel ban against some Muslim-majority nations. While that ban was challenged in court, the Supreme Court ultimately upheld the president’s authority to enforce the ban.

“It’s illegal,” according to Reena Arya, a senior attorney with the Catholic Legal Immigration Network. The Immigration and Nationality Act, she said, specifically states that anyone who enters the United States can apply for asylum, regardless of how they arrive.

“We need people in our country, but they have to come in legally and they have to have merit,” Mr. Trump said.

“Where does he get his legal authority to do something like this? He doesn’t have it,” Ms. Arya said.

In response to the president’s action, the American Civil Liberties Union, the Southern Poverty Law Center and the Center for Constitutional Rights filed a lawsuit against the Trump administration on Friday, The Hill reports.

“Neither the president nor his cabinet secretaries can override the clear commands of U.S. law, but that’s exactly what they’re trying to do,” Omar Jadwat, the director of the A.C.L.U.’s Immigrants’ Rights Project, said in a statement. “This action undermines the rule of law and is a great moral failure because it tries to take away protections from individuals facing persecution—it’s the opposite of what America should stand for.”

Rules around asylum seeking are not only a matter of U.S. law. In 1948, the United Nations recognized the right of individuals to seek asylum from persecution in other countries. According to its 1951 convention on refugees, the U.N. prohibited asylum seekers from being detained simply for seeking asylum. The convention also recognized that seeking asylum may require individuals to “breach immigration rules.”

“Where does he get his legal authority to do something like this? He doesn’t have it,” Ms. Arya said.

“Refugees are going to countries all over the world,” Ms. Arya said. “They are given an opportunity to apply for asylum. To be considered a refugee, according to the Immigration and Nationality Act, a person would have experienced persecution or a well-founded fear of persecution on account of race, religion, nationality, membership in a particular social group or political opinion.”

The president’s proclamation comes in part as a response to the migrant caravan, a group of thousands of Central Americans who are making their way through Mexico toward the United States. Reports of the actual number vary, with thousands having already accepted worker visas or asylum from Mexico.

“The arrival of large numbers…will contribute to the overloading of our immigration and asylum system and to the release of thousands…into the interior of the United States,” Mr. Trump said in the directive. More than 330,000 applied for asylum in the United States in 2017, according to the Associated Press, nearly double the number two years earlier and surpassing Germany as highest in the world.

Nevertheless, it has been more difficult to obtain asylum in the United States under the Trump administration. In April, Secretary of Homeland Security Kirstjen Nielsen said the administration would address “the rising level of fraud that plagues our system,” noting an increase in asylum claims overall in the last five years, including claims from families and unaccompanied minors.

Last year, the Trump administration changed the threshold that establishes a “credible fear” justifying asylum status. According to Clinic, asylum seekers now have to establish that their story is credible by a higher standard of a “preponderance of evidence” rather than the lower standard of “significant possibility.” 

Material from the Associated Press was used in this report. This story has been updated.

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J.D. Long García is a senior editor at America.