The tech industry and privacy advocates have found themselves at odds lately, but they're on the same side when it comes to a hotly contested Supreme Court case, which will decide whether the Trump administration can ask people if they are US citizens on the 2020 Census. On Tuesday, the nine justices of the court will hear arguments in that case, which pits the Department of Commerce against the State of New York.

The Department of Commerce, which oversees the Census Bureau, argues that the question is crucial to enforcing voting rights laws. The bureau hasn't asked a citizenship question of all households since 1950, but this White House is particularly focused on immigration issues. Indeed, court documents show that immigration hard-liners, including former White House chief strategist Steve Bannon, discussed adding the question in the earliest days of Trump's presidency.

But the move has drawn fierce opposition from all corners---including the Census Bureau's own chief scientist, who warned in a 2018 memo that adding the question "harms the quality of the census count." The overwhelming fear, backed up by the bureau's researchers, is that non-citizens will be afraid to answer honestly and either skip the Census or provide inaccurate information.

Issie Lapowsky covers the intersection of tech, politics, and national affairs for WIRED.

In advance of the hearing, the Supreme Court has received dozens of briefs from groups arguing against the citizenship question. Educators worry about how inaccurate data will impact the allocation of federal funding in schools. Voting and immigrant rights groups emphasize that accurate census data will be key to ensuring that voting districts are drawn fairly in 2021. Among the most vocal critics are groups representing the tech industry and privacy advocates. Business leaders say that the inclusion of a citizenship question will taint valuable data that they rely on, while privacy groups argue that the government hasn't done the bare minimum to vet the impact of collecting that information.

On the privacy side, the nonprofit Electronic Privacy Information Center, or EPIC, filed a brief along with an array of academics and privacy advocacy groups, arguing that the Census Bureau has failed to conduct a so-called privacy impact assessment, which is mandated by the E-Government Act of 2002. These assessments are supposed to include an analysis of what information is being collected, why it's being collected, its intended use, who it will be shared with, and how it will be secured, among other things.

These assessments are crucial, EPIC argues, because census data has been abused in the past. During World War I, it was used by the Department of Justice to enforce the draft. During World War II, it was used to identify Japanese-Americans for internment camps. After the September 11 attacks, the Census Bureau gave the Department of Homeland Security information to track Arab American populations in the United States—a development that only came to light through a 2004 Freedom of Information Act lawsuit, filed by EPIC.

Despite these concerns, the Census Bureau has completed no such assessment on the citizenship question. Instead, in a recent privacy impact assessment on the Census, the bureau fleetingly mentioned it would collect citizenship data at all. Not only that, but the assessment notes that all the data may be used for "criminal law enforcement activities" and may be transferred in bulk to other federal agencies.

"Our position is that collecting citizenship information from every person in the country and transferring it in bulk to another federal agency, potentially for criminal law enforcement, is a gross invasion of privacy that isn't justifiable," says John Davisson, counsel at EPIC.

The organization filed a lawsuit in the US District Court in Washington, DC, laying out much the same argument. The judge in that case found that while it's true the bureau has not completed the assessment, it still has time to do so before the census actually begins collecting the information. EPIC is appealing that decision in a hearing that will take place next month. The Department of Commerce didn't respond to WIRED's request for comment.

"Collecting citizenship information from every person in the country and transferring it in bulk to another federal agency, potentially for criminal law enforcement, is a gross invasion of privacy." John Davisson, Electronic Privacy Information Center

Meanwhile, members of the business community—including tech firms like Uber, Lyft, and Box—have laid out their own issues with the citizenship question in a separate brief, filed in advance of Tuesday's arguments. It argues that the companies represented rely on census data to make business decisions---such as which new markets Warby Parker wants to enter and where Uber chooses to deploy its electric bike share program. "Accurate data helps businesses take risks on changing and developing neighborhoods," the brief reads. "Unreliable data might mean businesses will open fewer locations in new communities, depriving businesses of new markets and communities of new stores or services."