President Donald Trump’s attempt to exclude undocumented immigrants from census figures that will be used to determine congressional apportionment has been challenged in federal court — the first of what experts believe could be many legal battles for the administration’s order.

The watchdog group Common Cause, along with the cities of Atlanta and Paterson, New Jersey, and other plaintiffs, filed a lawsuit Thursday in District of Columbia federal court, arguing that Trump’s effort “flouts the plain language of the constitution” and tries to do with a memorandum what should take a constitutional amendment. Other groups have also said they plan to challenge Trump’s memo, which he issued Tuesday.

“The President is not free to substitute his own personal judgment for those that have already been made by the Congress that enacted [apportionment law] and by the framers and ratifiers of [the constitution] and the Fourteenth Amendment,” the lawsuit said.

Trump’s memo would exclude undocumented immigrants from the process of divvying up the 435 House seats among the states. Census results are also used for legislative mapmaking, business decisions and guiding more than $1.5 trillion in government spending each year.

Trump, who has emphasized divisive immigration policy throughout his political career, said undocumented immigrants should not be included in the apportionment totals.

“My Administration will not support giving congressional representation to aliens who enter or remain in the country unlawfully, because doing so would create perverse incentives and undermine our system of government,” he said in a statement after he issued the memo. “Just as we do not give political power to people who are here temporarily, we should not give political power to people who should not be here at all.”

There are few Supreme Court cases “on point” about who to count in reapportionment, according to Loyola Law School professor Justin Levitt, a Justice Department lawyer during the Obama administration. But that doesn’t necessarily work in the administration’s favor. 

Decades of Supreme Court cases on redistricting treated apportionment by total population as a matter of fact, Levitt said.

“It’s a little weird because it’s not quote-unquote directly ‘on point,’” Levitt said. “But only because nobody thought that the basic understanding in place for 200 years was subject to question.”

The lawsuit filed Thursday alleges that Trump’s memorandum breaks with more than 200 years of precedent and legal advocacy around apportionment. The complaint cites a 1989 letter from the Justice Department to Congress — when current Attorney General William Barr served as head of the Office of Legal Counsel — stating that the Constitution required undocumented immigrants to be counted.

The complaint also tied the memorandum to Trump’s previous effort to add a citizenship question to the 2020 census and a broader strategy to “manipulate the census and apportionment process to deprive immigrants and racial and ethnic minorities of political power.”

Last year, Trump dropped an effort to add a citizenship question to the census after a Supreme Court ruling found it “pretextual” and violated administrative law. 

In response, Trump issued an executive order for the Census Bureau to collect information about the citizen voting age population through administrative records, which is a different segment of the population than undocumented immigrants.

The administration has not said how it plans to count the nation’s undocumented population, though. The Census Bureau referred questions about logistics to the White House, which has not responded to other questions. 

During a hearing Wednesday in a different case, the Justice Department’s Stephen Erlich said, “It’s really anyone’s guess at this point, we’re still formulating that, and there may need to be some modeling” of the undocumented population.

That may run into a Supreme Court precedent from 1999, which tossed statistical adjustment of census results to correct for undercounts. House Republicans in particular argued for years against the method, and the Supreme Court ruled that apportionment must be based on the actual count.

“I always hesitate to point out ironies like that because there’s so much uncertainty at this point who this does or does not help,” Levitt said. “It is clear that the president believes this helps him. It is not at all clear that the count of the population, minus undocumented individuals, helps Republicans.”

Fallout in other courts

Trump’s memorandum may actually strengthen an ongoing legal challenge to the executive order on collecting citizenship records. In a hearing Wednesday on that case, U.S. District Judge Paula Xinis in Maryland said the challenge to Trump’s order on citizenship data may have been too tenuous to proceed because it assumed states would change their own laws to draw legislative lines based on citizenship.

Xinis pointed out that some states, like Arizona, have statutes that automatically use apportionment data for mapmaking — data that would be affected by Trump’s memorandum because it would exclude undocumented immigrants.

“That to me suggests that this new executive order really changes the landscape, even of the current claims,” Xinis said.

Later, the judge allowed the groups challenging the collection of citizenship data to amend their complaint to include the new memorandum.

A federal court in Alabama has been considering whether to include undocumented immigrants in apportionment for two years. Rep. Mo Brooks, R-Ala., and the state government filed a suit there in 2018 arguing that including undocumented immigrants violated federal law.

The judge in that case has asked the litigants to explain in filings next month how the memorandum affects the case. In 2019, more than a dozen states, the Mexican American Legal Defense and Educational Fund and major cities intervened in the case, arguing the administration may not fully defend the inclusion of immigrants in census results.