How is an Unregistered Trademark Enforced

[Katydog]

If an app on the Apple store does not have a registered trademark, how can the owner determine the regional market that it can claim under a common law trademark?

[jk]

If an app on the Apple store does not have a registered trademark, how can the owner determine the regional market that it can claim under a common law trademark?

An entity generally holds trademark rights in the geographical area which it engages in business using the trademark. With an app, it could arguably be anywhere and everywhere.

Of course, if there are others using the same mark or a confusingly similar mark, there would be an issue of who used the mark in any given area first. They are likely to hold the rights in that area.