Epic Games is going after Apple (AAPL  ) with an Antitrust lawsuit following the removal of Fornite from the Apple App Store. Concerns over Apple's app store practices led Epic Games and other companies to protest Apple amid an ongoing antitrust investigation by the European Commission.

Epic Games filed a lawsuit against Apple on Thursday after the abrupt removal of the popular battle royale game Fortnite from the Apple App Store. Epic's complaint alleges that Apple's app store is a monopoly and that the company's stipulations for the app store are anticompetitive. Specifically, the lawsuit centers around app distribution and in-app payments. Epic later filed a similar lawsuit against Google (GOOGL  ).

Fortnite's removal was prompted by Epic's inclusion of a serverside payment system in a recent update, which circumvents Apple's own payment system and prevents the company from taking its commission from any in-app purchases.

In the past, Epic has made its disdain for Apple's practices well known, especially its 30% cut on all in-app purchases. In June, Epic joined with Match Group (MTCH  ) and other app developers in protest of Apple, voicing their support for an antitrust investigation that had been launched by the European Commission. The investigation is looking into similar claims as those currently being made by Epic in its California lawsuit regarding Apple's alleged app store monopoly.

"Epic is not seeking monetary compensation from this Court for the injuries it has suffered. Nor is Epic seeking favorable treatment for itself, a single company. Instead, Epic is seeking injunctive relief to allow fair competition in these two key markets that directly affect hundreds of millions of consumers and tens of thousands, if not more, of third-party app developers." Epic said of the latest effort.

While legal troubles are nothing new for Apple, some experts at least seem to think that Epic's lawsuit could be successful. Sandeep Vaheesan of the Open Markets Institute argued that the company had "detailed factual allegations" in its filings and that it relied on "strong legal theories" for the framework of its argument.

"[Epic is] challenging the practices by which [Apple and Google] acquired this dominant position and tried to leverage this dominant position into new markets. This is a major lawsuit." Vaheesan said to Polygon.