The European Competition Commissioner Margrethe Vestager has concluded several investigations against US technology companies in recent years. Many of these investigations were started under her predecessor, but under her leadership, the EU imposed fines on Google, ordered Apple to repay 13 billion euros in allegedly unpaid taxes to Ireland, and this year imposed a fine of almost 1 billion euros on Qualcomm Inc. for payments to Apple, which the EU considered illegal.

Since 2010, when the EU started to investigate Google's alleged abuse of its dominant search engine and later its Android operating system, Brazil, India, and Russia have launched their own antitrust investigations against the company. Russia and India have imposed fines. (Google has settled the case in Russia and is considering whether to appeal in India.) Four Brazilian investigations against Google are still pending.

The European Union has established itself as one of the world's strictest enforcers of antitrust law in recent years. At the technological level, Brussels and individual European governments have targeted companies in areas such as competition, taxation, data protection, and hate speech. European countries are preparing to enforce strict new data protection legislation, and EU regulators are increasingly interested in the potential abuse of data and algorithms.

The USA, which has lightly regulated the internet for years, is now beginning to reconsider its approach. In recent weeks, outrage over the revelation from Facebook Inc. that a British firm improperly accessed and retained information on millions of Facebook users has spurred both federal and state agencies to initiate investigations against the social media company and raised the prospect of new US legislation. Facebook CEO Mark Zuckerberg will appear before a House committee next week.

Vestager, a 49-year-old Dane, has become the public face of Europe's efforts to curb technology firms and the de facto global regulator for US tech giants. Her approach to companies like Google and Apple Inc. has made waves worldwide and influenced regulatory actions not only in the USA but also in countries such as Brazil, India, and Russia.

Vestager has used this power to extend antitrust law to the problems of the internet age. In her decisions, she emphasized the EU legal doctrine that dominant companies have a special responsibility not to abuse their power.

This differs from the approach of US antitrust authorities, who advocate intervening against companies only in cases where consumers are harmed, to avoid stifling innovation, especially in the digital space. "Where there is no demonstrable harm to competition and consumers, we are hesitant to impose special obligations on digital platforms," Makan Delrahim, head of antitrust at the Justice Department, said recently in a speech in Brussels.