While U.S. courts took significant steps to relax domestic antitrust policy in 2007, European competition regulators stepped into the gap and emerged as the world’s most aggressive antitrust watchdogs.

The hallmark of the EU Competition Commission’s hard-line approach is the nearly $700 million fine it imposed against Microsoft in 2004 for the bundling of its Windows Media Player with its operating system, and its failure to share server interoperability information with competitors.