Keith N. Hylton, March 20, 2016
United States v. Microsoft Corp. (Microsoft III) is now fifteen years old, and that I would write such a long introduction to a reprint of significant portions from the opinion is a sign its significance has not died out. Just the opposite, I think it will become more significant in the near future, and not only because of its impact on U.S. antitrust law. The decision lays the groundwork for international enforcement of antitrust in high technology markets, at least as we have come to know them, and this is likely to continue to be significant for the foreseeable future.
As for U.S. law, it has become increasingly clear that Microsoft III is the second most important monopolization decision after Learned Hand’s United States v. Alcoa. To be sure, Alcoa must and will always be the most important Section 2 opinion because it sets the foundational principles for modern (post-1945) monopolization law. Judge Hand overturned a doctrinal framework that had induced a passive approach to antitrust enforcement against dominant firms and replaced with a framework that enabled and encouraged aggressive antitrust enforcement. Microsoft has had a comparatively limited impact, but it clarifies and updates the monopolization standard and constrains judges, and in these senses fundamentally alters the law from Alcoa.