United States v. Microsoft (1998-2001)
The Justice Department sued Microsoft for using its Windows monopoly to crush Netscape and other browser rivals. Judge Thomas Penfield Jackson ordered Microsoft broken up; an appeals court reversed but upheld the underlying liability finding.
Microsoft settled in 2001 with a consent decree that required it to share interoperability information and let computer makers configure Windows more freely.
The case became the model for tech antitrust. A dominant platform that tilts the playing field against its own customers faces real enforcement risk.
Arm's situation parallels Microsoft's. A dominant platform that millions of products depend on starts competing with the developers that license its technology. The same legal theory applies: using a foundational position to advantage a downstream business.
