Privacy-focused software provider Proton, makers of Proton Mail, Proton Calendar, Proton Drive, and other apps, has sued Apple, alleging anticompetitive practices in Apple’s App Store. In the new lawsuit, Proton says the iPhone maker holds a monopoly in the smartphone, app distribution, and app payment processing markets. It also compares Apple’s fees to tariffs on internet commerce, calling them “artificial and arbitrary.”

The suit is looking for changes to the App Store and monetary damages, which Proton says will be donated to organizations fighting for democracy and human rights.

The court papers, filed in the Northern District of California, are a part of a larger class-action suit against Apple. Proton says it’s joining other developers, including a group of Korean developers, who are also suing the tech giant.

The suit is among the latest to challenge Apple’s chokehold on the mobile app market.

It follows another yearslong battle between Epic Games and Apple, which Apple largely won as it was declared not to be a monopoly, setting a precedent for the new lawsuit to argue against. However, the judge in that case also ruled that Apple must let U.S. app developers link to their websites where they offer alternative payment mechanisms, without charging a commission on those sales. (Apple is still fighting this matter on appeal.)

Proton’s case takes a different angle. It cites the Epic case, saying that the evidence proved that Apple makes such a large profit on App Store fees that it questions whether the fees are really necessary to support the maintenance of the App Store, as Apple claims.

Proton, similarly, takes issue with Apple’s policies around payments. It points out how Apple barred developers from talking directly to their customers in the app, where they could inform them of discounts on the web. In addition, apps that don’t support Apple’s payment system are at risk of being removed from the App Store, the suit states.

The arguments around payments delve into other nuances about how the system works, like how it’s harder to manage payments and subscriptions across devices because of Apple’s rules. For instance, the company explained in a blog post that customers who upgraded their accounts on the web can’t downgrade from their iOS device, which is a poor customer experience.

Proton also argues that its Calendar app can’t be set as the default, although iOS allows users to swap out the defaults for other apps like browsers, email, phone calls, messaging, and more. And it notes that its Proton Drive is restricted from background processing, whereas iCloud is not.

Notably, Proton’s case focuses on how Apple’s single point of distribution with the App Store makes it a tool used by dictatorships around the world to silence free speech. On this front, it points to all the apps Apple has to remove to comply with laws in markets like Russia and China. That decision trickles down to iOS developers, Proton says, like when its VPN app was threatened with removal because it claimed to “unblock censored websites.”

“Apple’s monopoly control of software distribution on iOS devices presents a myriad of problems for consumers, businesses, and society as a whole,” Proton’s post reads. “Anti-monopoly laws exist because the power gifted by monopoly status inevitably leads to abuse. In the case of oligarchic tech giants, these abuses have wide implications for society, and it’s vital to the future of the internet that they be addressed now.”

We reached out to Apple for comment and did not immediately hear back.