In claims submitted to CAT in December last year, which have only just surfaced, Epic alleges that both Apple and Google abused their "dominant position" in the iOS and Android app distribution market by "unfairly restricting competition" and "reserving to [themselves] the sole payment processing mechanism for purchases of in-app content."
It also claims both companies used their market position to "charge unfair prices for the distribution of apps," adding that each firm has "engaged in anti-competitive agreements/concerted practices in the UK and EU."
With that in mind, Epic is asking CAT to provide various forms of relief, including ordering both companies to restore Fortnite to their app stores and remove restrictions relating to the use of alternative payment methods.
It's also seeking "such further or other relief as the Tribunal may think fit," although it hasn't explicitly asked for monetary damages.
So, what's the bottom line here? Simply put, Epic is attempting to convince UK regulators that Apple and Google were wrong to pull Fortnite from sale on iOS and Android when the company chose to break marketplace rules by implementing a third-party payment option.
It's the same argument the company is making in the United States, where Epic and Apple's long-running dispute is expected to come to a head when it heads to trial in May this year.
Commenting on that case, Judge Yvonne Gonzalez Rodgers said the outcome could have "serious ramifications" for other major platform holders like Sony, Nintendo, and Microsoft.