The House came to the Supreme Court to argue against the Trump administration’s plan to add a citizenship question to the 2020 Census — and ended up getting quizzed about why lawmakers didn’t take their own action if they wanted to stop it.

In about 90 minutes of lively questioning Tuesday, the conservative majority of the court appeared ready to defer to Commerce Secretary Wilbur Ross’ decision to add the question even though it could reduce census responses among noncitizen households.

[Supreme Court to decide whether LGBTQ people are covered by Civil Rights Act]

The case is one of the most significant for members of Congress during the current Supreme Court term because the results determine how many House seats each state gets, how states redraw congressional districts and the distribution of billions of dollars from federal programs to states and local governments.

House General Counsel Douglas N. Letter’s 10-minute slice of argument time started out pleasantly enough. Letter passed on Speaker Nancy Pelosi’s thanks to the court for allowing the lawmakers a rare chance to address the court directly, and Chief Justice John G. Roberts Jr. replied: “Tell her she’s welcome.”

Letter then told the justices that accuracy of the census was of utmost importance to the House, and the Trump administration wasn’t following the law or the Constitution because it would reduce the actual count of people in the country.

“Anything that undermines the accuracy of the actual enumeration is immediately a problem,” Letter said. He added that Ross’ reason for the question — that the Justice Department wanted more accurate information to enforce the Voting Rights Act — was outside of the purpose for conducting the census.

But soon the justices turned to congressional inaction. First, Justice Ruth Bader Ginsburg pointed out that Congress has primary control over the census, and has been alerted to the citizenship question for more than a year “and has done nothing about it.”

“So one question is who should decide?” Ginsburg said. “Congress is silent. Should the court then step in?”

[House gets its say as Supreme Court takes up census citizenship question]

Letter responded by describing how Ross and a Justice Department official have been called before Congress to explain the decision, yet they declined to answer because of the ongoing litigation now at the Supreme Court.

If Congress is supposed to step in, “obviously the House needs the information,” Letter told the justices. “And yet we’re being told we can’t have the information because it’s only for you.”

Roberts then pointed out that the challengers already contend there was no basis for Ross to make the decision, and there’s no room for him to use his discretion to add the question. “So what more information does the Congress need to address the problem?” Roberts asked.

Letter replied that the House wants to know whether this was just a political decision.

That prompted Justice Brett M. Kavanaugh to build on Ginsburg’s question, and ask: “Why doesn’t Congress prohibit the asking of a citizenship question in the same way that Congress has explicitly provided that no one can be compelled to provide religious information?”

Congress could attempt to do that, Letter said, “but, as we know, that doesn’t stop this court from interpreting the statute and the Constitution.”

During the full argument, justices on the liberal wing of the court repeatedly questioned the reason for Ross’ decision, highlighting how the Commerce Department had asked the Justice Department for a justification.

[Supreme Court skeptical on stopping partisan gerrymandering]

Justice Sonia Sotomayor called it “a solution in search of a problem.” Justice Elena Kagan called it “shopping for a need.” Justice Stephen G. Breyer pointed to a Census Bureau expert who said the citizenship question would reduce census responses among noncitizen households by about 6.5 million people, and end up with less accurate data than using statistical models.

But justices on the conservative wing of the court, particularly Justice Samuel A. Alito Jr., questioned whether Ross’ decision met the legal test of arbitrary and capricious because those statistical models hadn’t been created when Ross made the decision.

And Kavanaugh and Justice Neil M. Gorsuch pointed out repeatedly that the question has been used off and on in previous censuses and Congress gave discretion to the Commerce Department to create the form.

Roberts pointed out that the principal purpose of the census form is to count people, but it has been “quite common” to ask other demographic questions.

“Sex, age, things like that,” Roberts said. “You go back and it looks, you know, do you own your house? Do you own a radio? I mean, the questions go quite beyond how many people there are.”

The Supreme Court will make a decision by the end of June, which is not only when the current term ends but also the deadline for the government to finalize the census questionnaire.

New York Democrat Carolyn Maloney, a co-chair of the House Census Caucus and author of a bill to block such a citizenship question, attended Tuesday’s argument.