As Washington D.C. institutions go, Public Citizen rates among the more anodyne. Started in the early ‘70s by Ralph Nader, the group is known for its liberal-minded crusades on such unglamorous topics as campaign finance reform and consumer safety.

But for some period of time over the past few years, Public Citizen found its website being categorized as—well—porn by an internet filtering service used by a major government agency.

Since April, Public Citizen has been in litigation with the Department of Education over what it claims to be a violation of its First Amendment rights. At issue was a truly bizarre and unexpected revelation that took place earlier in the year when officials with the group visited the department to discuss separate matters.

Attempting to access their own website from the Department of Education’s WiFi network, Public Citizen attorneys realized they were being blocked from doing so, with a note popping up that said accessing www.citizen.org was “in violation of your Internet usage policy”

At first, they thought it was a bit of vindictiveness from a department whose secretary, Betsy Devos, they had been targeting—an attempt by the agency to use control over its network to silence critical voices.

In February, they filed a Freedom of Information Act request for more information, but that proved unsuccessful. So they filed a lawsuit instead. And in the course of litigation they discovered the actual answer to the blackout: the Department’s web filtering company was categorizing them as an “advocacy organization”—which they are—and, for some inexplicable reason, advocacy organizations were being placed under the “adult/mature content” categorization, right alongside porn and gambling.

“It was bizarre,” said Nandan Joshi, Public Citizen’s lawyer.

The company responsible for all this is Fortinet, which provides network and content security to companies and government entities. According to federal procurement data, Fortinet has done work for a host of government agencies—including the Defense Department, the Interior Department, the State Department, and the Environmental Protection Agency. It is unclear from that data what services it provided beyond information technology and security products. But for the Department of Education, the company’s role was to ensure that unsavory or problematic content could not be accessed from its network.

To do that, Fortinet applied (as it does for other clients) classifications for specific websites and then broader categories to those specific classifications.

What methodology it uses for this is unclear. But when Public Citizen became privy to it months into the legal process, it struck the folks there as decidedly confusing. According to its own database, Fortinet listed Public Interest Research Groups—which, like Public Citizen, is a liberal-minded interest group—as a “General Organization” as opposed to an advocacy organization. More confusing was why Fortinet decided that so-called “advocacy groups” needed to be placed under the adult/mature content category at all.

In search of a resolution, the Department of Education first informed Public Citizen that it was “whitelisting” its website so that it no longer got caught up in their security filters. When Public Citizen became more fully aware of what was happening with those filters, they sought to have Fortinet take "advocacy organization” out of the “Adult/Mature” content category.

Department of Education agreed to ask Fortinet not to block advocacy groups on the Department’s networks. And, as a result, Public Citizen announced on Thursday that it was dropping its lawsuit against the department. But even though the group is no longer bringing legal action, Joshi said they weren’t exactly satisfied. There was, he noted, no way to know if other groups were also having their website blocked because Fortinet was listing them as “advocacy organizations” and, therefore, subjecting them to the “adult/mature” filter. They are calling on the company to simply end the practice of putting advocacy organizations under that categorization.

“It is possible this problem still exists but we just don’t know about it,” said Joshi. “It is a little bit scarier in that the effects are broader. Some web filterer decides to do a classification and all the sudden voices are silenced.”

With reporting by Lachlan Markay