Epic Games Inc. expanded its antitrust legal fight with Alphabet Inc.’s Google by accusing the tech giant of conspiring with Samsung Electronics Co. to block rival app marketplaces through default settings on mobile devices sold all over the world.

While it’s turned on, it automatically keeps users from installing apps unless they come from “authorized sources” — namely, Google and Samsung’s app stores. Epic claims there’s no process for any rival store to become “authorized.

Epic has today announced major new litigation as it takes its battle against existing app store monopolies to former ally Samsung, as well as continued rival Google, in a fresh front that may see a return to the courtroom.