Seven people were arrested Wednesday night in Arizona as they attempted to block the deportation of Guadalupe García de Rayos.

Rayos, as the New York Times reported, is a citizen of Mexico who has been living in the United States without documentation since 1996. Over that period, she had two children, both American citizens. She was arrested in 2008, the Los Angeles Times reported, after she was found to be working illegally at an amusement park in Mesa, Ariz.

In 2013, the Department of Justice issued a removal order for Rayos, but she was allowed to remain in the country with the stipulation that she checked in with the Department of Homeland Security’s Immigration and Customs Enforcement every six months. During that regular visit Wednesday, she was detained, and the government began deportation proceedings. As a van carrying Rayos left the facility, protesters blocked its progress, resulting in the arrests.

This scenario — a parent who’d lived in the country for decades suddenly facing deportation — is one that President Trump’s opponents imagined becoming far more common were he elected. This is both an isolated incident and an example of something that’s happened with regularity over the past several decades. Former president Barack Obama’s proposed protection program announced in November 2014 would probably have protected people in situations like Rayos’s, though, as would his executive order directing ICE to prioritize immigrants with criminal backgrounds.

Trump, though, has promised a much wider net. His executive order, signed five days into the job, included a determination that administration policy would be to “remove promptly those individuals whose legal claims to remain in the United States have been lawfully rejected, after any appropriate civil or criminal sanctions have been imposed.” An attorney for Rayos said on a conference call that Sen. John McCain (R-Ariz.) sought to intervene on her behalf, but the power lies with the executive branch.

The Los Angeles Times looked at Trump’s order and estimated that some 8 million people might be subject to deportation under its strictures. We were curious how many might be subject specifically to the scenario Rayos faced: complying with instructions to check in with ICE only to be deported under an outstanding order.

As it turns out, that’s a very hard number to estimate, thanks to the murky way in which such orders are issued — and thanks to foot-dragging from the government.

Susan Long is co-director of the Transactional Records Access Clearinghouse (TRAC) at the Syracuse University and a faculty member of the Whitman School in Management. TRAC compiles detailed data on immigration that it has received from Freedom of Information Act (FOIA) requests from the government. That includes data on removal orders from immigration court and the actual number of people removed or returned each year. (There’s a distinction between those two things; the former is what we generally think of when we think of deportations.)

Those data, for the years available, look like this.

What we might expect to see is that the number of orders is larger than the number of removals. After all, we’re considering a situation in which a person with a standing deportation order hadn’t yet been removed. But instead the data indicate far more removals than orders over the past decade or so. (The numbers are calculated by fiscal year, and numbers for 2016 and 2017 are incomplete.) One reason is that the same people can be removed multiple times — but that’s not the main reason.

If your assumption is, instead, that this is because ICE removed people under years-old orders, that’s incorrect, according to TRAC’s Long. When I told her I was hoping to figure out how many outstanding orders there were, she laughed.

“Increasingly, removal orders bypass the immigration court,” she explained. In a nutshell, that’s why the numbers in the chart above appear to be flipped: Many orders for removal don’t go through immigration court at all; instead they’re being issued through the Department of Homeland Security.

“That obviously poses some challenges,” she said with understatement. Determining how many additional orders have been issued requires getting that data from the government, which TRAC has tried to do.

“ICE contends — I’m sure it’s false — that they can’t identify the source of the removal orders,” she said of my question about how non-court orders have been issued. As for the grand total of non-court orders? “I’m not sure ICE actually knows, itself,” she said. We’re talking about years of orders that may or may not have been appealed, for example, which can be hard to track down.

ICE, in Long’s experience, has little interest in doing so anyway.

“It’s taken hundreds of requests and litigation” to get the information they have, she said, noting that they’ve been involved in a long-standing lawsuit against the agency. “Now they’re refusing to release information that would allow you to update this,” she said — an obstruction that began in the last few months of the Obama administration. “They contend that what they released in the past was voluntary and while they don’t contend that these things are exempt [from FOIA], they aren’t providing them.”

A call to the Department of Homeland Security was not returned.

“It’s really a problem to monitor what’s going on in any sort of comprehensive way, because of the unwillingness of the agency,” Long said. “It isn’t interested in transparency.”

As this story was being written, reports emerged that Rayos had been deported. If so, she may be the first of thousands more — though the number of thousands that should go in that sentence is impossible to determine from outside the walls of the U.S. government.