In the United States the courts have consistently said this determination is based on how much market power the competitor wields:
Of course where the seller has no control or dominance over the tying product so that it does not represent an effectual weapon to pressure buyers into taking the tied item any restraint of trade attributable to such tying arrangements would obviously be insignificant at most. As a simple example, if one of a dozen food stores in a community were to refuse to sell flour unless the buyer also took sugar it would hardly tend to restrain competition in sugar if its competitors were ready and able to sell flour by itself. (https://casetext.com/case/northern-pac-r-co-v-united-states)
Whether Apple has enough dominance over the smartphone market to cause an unreasonable restraint of trade in the app distribution market is up to a court to decide at this point.
Of course where the seller has no control or dominance over the tying product so that it does not represent an effectual weapon to pressure buyers into taking the tied item any restraint of trade attributable to such tying arrangements would obviously be insignificant at most. As a simple example, if one of a dozen food stores in a community were to refuse to sell flour unless the buyer also took sugar it would hardly tend to restrain competition in sugar if its competitors were ready and able to sell flour by itself. (https://casetext.com/case/northern-pac-r-co-v-united-states)
Whether Apple has enough dominance over the smartphone market to cause an unreasonable restraint of trade in the app distribution market is up to a court to decide at this point.