It’s unusual for Twitter to ban specific advertisers, but on Friday, the social media giant announced it had made a large exception. Twitter banned ads from Kaspersky Lab, the Moscow-based cybersecurity company, citing the U.S. government’s claims that the firm’s CEO Eugene Kaspersky has ties to Russian intelligence agencies.

Earlier on Friday, Kaspersky tweeted from his personal account to publicly confront Twitter about the ban. Kaspersky included an open letter to Twitter CEO Jack Dorsey asking for more transparency, since the ban was quietly enacted without an announcement. Kaspersky claims the company was alerted of the ban via “a short letter from an unnamed Twitter employee” in early January and wanted public confirmation from the company with more details.

“One thing I can say for sure is this: we haven’t violated any written — or unwritten — rules, and our business model is quite simply the same template business model that’s used throughout the whole cybersecurity industry: We provide users with products and services, and they pay us for them.” Kaspersky’s letter doesn’t mince words and suggests the firm leader took things personally. “You’re only shooting yourself in the foot when you cater to the geopolitical noise and start refusing to promote material on false pretenses — contrary to the interests of your own business (how else can we describe not accepting money from clients that run ethical businesses?)”

Before Kaspersky Lab was banned, it alleged to have spent roughly $93,000 to promote its content on Twitter in 2017. In September, the U.S. Department of Homeland Security announced a ban on Kaspersky Lab for its ties to Russian intelligence, catalyzing a lengthy back and forth between the government and a foreign company. Kaspersky Lab responded by filing an appeal under the Administrative Procedure Act, arguing that the Department of Homeland Security acted unconstitutionally and violated the company’s right to due process. Still, the DHS maintains that Kaspersky Lab’s software could be used to enable Russian spying and thus its products should not be used in U.S. government networks. U.S. President Trump signed the ban into law in December.

It’s unusual for Twitter to quietly follow suit, especially without announcing the change. Department of Homeland Security cybersecurity official Jeanette Manfra told Reuters that her agency has not instructed U.S. companies to punish Kaspersky, and therefore Twitter decided to copy government policy on its own. Now that Kaspersky has made Twitter’s move public, it could convince other U.S. companies to act similarly.

Kasperksy maintains his company’s innocence and went so far as to accuse Twitter of political censorship. However, in the wake of Cambridge Analytica and the illuminated ways in which social media data can aid foreign operations, it’s clear why Twitter would want to limit its transactions with the firm.