Competition law is the field of law that promotes or seeks to maintain market competition by regulating anti-competitive conduct by companies. Competition law is implemented through public and private enforcement. Competition law is known as "antitrust law" in the United States. It is also known as "anti-monopoly law" in China and Russia, and in previous years was known as "trade practices law" in the United Kingdom and Australia. In the European Union, it is referred to as both antitrust and competition law.The history of competition law reaches back to the Roman Empire. The business practices of market traders, guilds and governments have always been subject to scrutiny, and sometimes severe sanctions. Since the 20th century, competition law has become global. The two largest and most influential systems of competition regulation are United States antitrust law and European Union competition law. National and regional competition authorities across the world have formed international support and enforcement networks.

Modern competition law has historically evolved on a national level to promote and maintain fair competition in markets principally within the territorial boundaries of nation-states. National competition law usually does not cover activity beyond territorial borders unless it has significant effects at nation-state level. Countries may allow for extraterritorial jurisdiction in competition cases based on so-called "effects doctrine". The protection of international competition is governed by international competition agreements. In 1945, during the negotiations preceding the adoption of the General Agreement on Tariffs and Trade (GATT) in 1947, limited international competition obligations were proposed within the Charter for an International Trade Organisation. These obligations were not included in GATT, but in 1994, with the conclusion of the Uruguay Round of GATT multilateral negotiations, the World Trade Organization (WTO) was created. The Agreement Establishing the WTO included a range of limited provisions on various cross-border competition issues on a sector specific basis.

AT&T Corporation, originally the American Telephone and Telegraph Company, is the subsidiary of AT&T Inc. that provides voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agencies.

During the Bell System's long history, AT&T was at times the world's largest telephone company, the world's largest cable television operator, and a regulated monopoly. At its peak in the 1950s and 1960s, it employed one million people and its revenue ranged between US$3 billion in 1950 ($35.1 billion in present-day terms) and $12 billion in 1966 ($99.1 billion in present-day terms).

In 2005, AT&T was purchased by Baby Bell and former subsidiary SBC Communications for more than $16 billion ($21.2 billion in present-day terms). SBC then changed its name to AT&T Inc. Today, AT&T Corporation continues to exist as the long distance subsidiary of AT&T Inc., and its name occasionally shows up in AT&T press releases.