Antitrust Litigation & Counseling


Our international reputation for excellence is based on successes in numerous high-profile antitrust cases. We were founded in 1994 as a boutique antitrust firm, and maintain our commitment to antitrust today.

We remain best known for our record-breaking accomplishments on behalf of plaintiffs. We nonetheless have substantial experience representing defendants — from Fortune 500 companies to small, family firms — in antitrust and commercial litigation.


  • We secured a $3.05 billion settlement (plus injunctive relief valued at between $25 and $87 billion) as lead counsel to a class of millions of retailers in their payment card tying claims against Visa and MasterCard.
  • We secured a $2.75 billion settlement on behalf of Discover Financial Services in a case challenging Visa’s and MasterCard’s exclusionary rules prohibiting U.S. member banks from issuing Discover credit and debit cards to their customers.
  • We have represented parties successfully in jury trials and antitrust cases.
  • We represent plaintiffs and defendants in some of the country’s largest current commercial antitrust cases.
  • We represent parties advocating for or challenging transactions and/or business practices before federal and state antitrust enforcement agencies.
  • We represent parties to multi-billion dollar transactions in merger review proceedings before federal antitrust enforcement agencies.
  • We counsel companies on all aspects of antitrust, including antitrust compliance programs, distribution arrangements, licensing agreements, agency business reviews, merger analysis, litigation risk assessment as well as issues related to standard setting groups and the interface between intellectual property and antitrust law.
  • We submit amicus curiae briefs on important antitrust issues to the United States Supreme Court and to appellate courts.


Constantine Cannon has litigated and counseled clients on antitrust matters that are relevant to a number of industries.

Among other things, Constantine Cannon has particular experience representing parties that participate in the following industries:

What Sets us Apart

Our attorneys are both experts in antitrust law and seasoned litigators. Our approach to every case, whether on the plaintiff’s side or the defense, is to be prepared to take the case to trial. Through technology, optimization of resources, and the specialized expertise of CAAS LLC, a consulting entity with which the firm has an existing relationship, we are able to contain the rapidly increasing costs of litigation better than other firms.

Counseling, Training and Investigations

Our counseling services include advising clients on the antitrust issues raised by certain business practices; enforcement agency investigations and business reviews; litigation risk assessment; merger analysis; management and employee training; advice on competitor collaborations, including joint ventures, standard setting organizations, and trade associations; and investigations into alleged antitrust violations.

Antitrust Today Blog Posts

FTC Reaffirms Focus on Labor Markets in Reviewing Microsoft-Activision Blizzard Merger

By Kristian Soltes Federal antitrust enforcers are heeding the call for more vigorous regulation of monopsonies, which may soon no longer be the forgotten man...

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The Antitrust Week In Review

Here are some of the developments in antitrust news this past week that we found interesting and are following.   Drivers’ Lawsuit Claims Uber and...

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The Antitrust Week In Review

Here are some of the developments in antitrust news this past week that we found interesting and are following.   Facebook owner Meta makes antitrust...

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Cydia is Getting a Chance to Prove its App Store Antitrust Claims Against Apple

By David Golden Cydia, the alternative iOS app store, has been given the chance to seek discovery to prove its antitrust claims against Apple. On...

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