Trump dropped the effort to add a citizenship question to the 2020 census on Thursday following a recent defeat in the U.S. Supreme Court. Instead, he ordered other federal agencies, including the Department of Homeland Security and Social Security Administration, to provide relevant data.
The Census Bureau can combine such information with citizenship data it receives from a population tally called the American Community Survey (ACS), which is based on a smaller sample than the once-a-decade census.
If states use citizenship data provided by the federal government to redistrict, it would likely shift power toward Republicans, as Reuters reported in April https://reut.rs/2G9v8to. But it would also trigger a new wave of litigation, some advocates and redistricting specialists said.
Potential plaintiffs could claim that citizen-only redistricting violates the 14th Amendment's Equal Protection Clause and other laws barring discrimination against minority groups.
The American Civil Liberties Union (ACLU) will "monitor and watch what the federal government is doing and be very vigilant for any redistricting issues that might arise," Sarah Brannon, managing attorney for the ACLU Voting Rights Project, said on a call with journalists on Thursday.
"We will sue as necessary," she said.
The White House did not respond to a request for comment on potential legal challenges.
Congress and state legislatures both rely on census data to determine how many political seats districts should get. As it stands, all residents count, regardless of citizenship or legal status.
But there has been a fierce political debate about whether that should change, especially in state districting.
In his remarks on Thursday, Trump noted that some states may want to draw state and local districts based on eligible voters. He has repeatedly said that asking residents about their citizenship status is important and should not be controversial.
The Mexican American Legal Defense and Educational Fund (MALDEF) would also sue if there is an attempt to use anything but a full population count to distribute political seats, the group's general counsel Thomas Saenz said in an interview.
Asian Americans Advancing Justice (AAAJ) is also keeping a close eye on developments, said its president John Yang.
Both groups and the ACLU have been plaintiffs in litigation regarding the proposed census citizenship question.
The Census Bureau must present redistricting data to state legislatures by April 1, 2021. But litigation could happen much sooner, experts said.
Before the Census Bureau sends information to states, it needs to file a notice in the Federal Register, triggering a comment period when advocates would likely raise objections, said Jeff Wice, a Democratic redistricting adviser.
Anything that "furthers the Trump administration's goal to weaken representation for immigrant populations" could be a trigger, he said.
Lawsuits could take many forms. Plaintiffs could sue legislative bodies that try to employ citizen-based voting maps, or may go after the Trump administration itself for providing the data.
One potential defense is a 2016 U.S. Supreme Court decision known as Evenwel.
In that ruling, justices rejected arguments from Texas Republicans that legislative districts should be based on the number of eligible voters. But the Court stopped short of ruling on whether a state could use metrics like citizenship to draw voting maps.
Many scholars have said Evenwel leaves the door open for a state to draw maps based on its citizen population.
The state of Alabama sued the federal government last year, arguing that congressional apportionment should exclude non-citizens.
Legal scholars see the case as a long shot, but U.S. Attorney General William Barr appeared to reference the lawsuit on Thursday.
"There is a current dispute over whether illegal aliens can be included for apportionment purposes," Barr said. "Depending on the resolution of that dispute, this data may be relevant to those considerations. We will be studying this issue."
In the meantime, New Jersey Senator and U.S. presidential candidate Cory Booker introduced a bill on Wednesday to block the Census Bureau from including citizenship data in the digital file it sends to states.