A federal judge in California has blocked the Trump administration from including a citizenship question on the 2020 census, ruling the decision to add the question is unconstitutional.

U.S. District Judge Richard Seeborg of the district court in San Francisco is the second federal judge to reject the Trump administration’s bid to include the citizenship question on the upcoming census questionnaire. It's a fraught political issue, with Democrats calling the citizenship question a thinly-veiled effort to supress counting of minorities — a charge Republicans roundly reject.

In January, U.S. District Judge Jesse Furman in Manhattan barred the Commerce Department from asking about citizenship on the census, ruling the decision to do so was illegal. The U.S. Supreme Court agreed last month to consider the issue, and the justices will hear arguments in the case out of New York in April.

In his ruling, Seeborg, an Obama appointee, said Commerce Secretary Wilbur Ross’s decision to add the question to the 2020 census violated both federal law and the Constitution’s Enumeration Clause.

“The record in this case has clearly established that including the citizenship question on the 2020 Census is fundamentally counterproductive to the goal of obtaining accurate citizenship data about the public,” Seeborg wrote in his 126-page decision. “This question is, however, quite effective at depressing self-response rates among immigrants and noncitizens, and poses a significant risk of distorting the apportionment of congressional representation among the states.”

Including the citizenship question on the census, Seeborg, added, “threatens the very foundation of our democratic system.”

The court said that the decision to include the citizenship question “represented an abuse of discretion” and said the Commerce Department conducted a “cynical search” to find a reason or an agency request to justify its addition to the 2020 census.

Ross announced in March 2018 that the citizenship question — “Is this person a citizen of the United States?” — would be included on the upcoming census in an effort to ensure better enforcement of the Voting Rights Act.

But the move brought swift legal challenges from states, cities, and immigrants rights groups which called for the courts to stop the Trump administration.

The states argued Ross’s decision to add the citizenship question violated federal law and the Constitution. Its inclusion, they warned, would lead to a population undercount that would disproportionately affect states and cities with large immigrant populations.