Although the US antitrust laws do use the language of monopoly, they are broadly drafted and have been subject to a lot of judicial interpretation. Rather than

Although the US antitrust laws do use the language of monopoly, they are broadly drafted and have been subject to a lot of judicial interpretation. Rather than monopoly, when considering antitrust questions it is sometimes better to think about "market power and … whether business conduct has or likely will have anticompetitive effects." [1] "Market definition is least useful when market shares would not be strongly probative of market power or anticompetitive effect, while direct evidence as to market power or anticompetitive effect is available and convincing." Apple's control of the App Store has a direct anticompetitive effect in the secondary market for iOS apps. This is pretty clear from the fact that Apple explicitly prohibits some apps that compete with its own. The interesting question is whether the plaintiffs will succeed in proving that Apple's conduct is illegal, under the prevailing interpretation of the US antitrust laws. [1]: Market definition: an analytical overview (2007). https://digitalcommons.wcl.american.edu/cgi/viewcontent.cgi?article=1278&context=facsch_lawrev https://digitalcommons.wcl.american.edu/cgi/viewcontent.cgi?...