Abstract

The US Supreme Court ruling in American Express represents a milestone for antitrust enforcement in two-sided markets. Not surprisingly, the ruling has sparked lively discussions in the antitrust law and economics community. After providing an overview of the arguments deployed by the Court as well as the amici curiae the article sheds light on the key principles of the decision (how the two-sidedness of platforms may affect the definition of the relevant market, the assessment of competitive effects and the relevance of undertakings' business models). By adopting a comparative approach, the paper draws a comparison with the EU legal landscape.