Praised for providing ‘practical, business-first advice’, the merger control team at Clifford Chance covers the full lifecycle of U.S. and cross-border reviews, from early-stage antitrust analysis through complex agency investigations and multi-jurisdictional clearance processes. The team advises on both contentious and non-contentious matters, with notable activity across the technology, healthcare, and energy sectors. Washington DC-based Leigh Oliver heads the U.S. antitrust practice and brings deep experience advising clients in highly regulated industries, supported by Joseph Ostoyich, who is a key name for litigation arising from merger challenges. Sharis Pozen’s background at the DOJ, FTC and in-house strengthens the team’s approach to merger clearance and investigations.
Legal 500 Editorial commentary
Testimonials
Collated independently by Legal 500 research team.
- 'Sharis Pozen is similarly well-known throughout the antitrust bar and brings the unique background of having been a law firm partner, government leader, and in-house executive. This team has some excellent up and coming lawyers on the team, including Jonathan Elsasser who specializes in healthcare antitrust.’
- ‘We have worked closely with Leigh Oliver in the DC office for almost a year. Leigh is an expert in healthcare antitrust, and is both personally and professionally dedicated to our organization's success. She has proven to be a strong advocate for our interests, and indispensable to addressing the many challenges facing our organization.’
- 'The individuals in the firm are exceedingly well organized and thus are able to manage document production without continuing relying on the in-house team to make things happen. Business people really like working with them because of the practical nature of their advice.’
- ‘Clifford Chance has an elite antitrust expertise with genuinely practical, business-first advice. Fast, clear, and outcome-focused. They have deep sector insights.’
- ‘The team is very response (which is one of the key qualities I seek in a firm). They are creative thinkers who collaborated with us to accomplish critical goals for the Company. Their understanding of DOJ is critical when dealing with DOJ and they translate that understanding into actionable advice.'
- ‘Leigh Oliver and Lauren Rackow combine real regulatory credibility with commercial instincts. They’re also brilliant at anticipating regulator angles early. They translate business goals into regulator‑ready narratives.'
- ‘Leigh Oliver and Michael Van Arsdall are accessible, willing to listen, and work with us to understand the business and translate that understanding into advice when dealing with DOJ. They delivered the goods in connection with a critical merger.'
- ‘The practice has deep expertise and boasts attorneys with decades of experience on the private side and in government. They are notable for cross-border clearance processes, with strengths in the US and globally, and for life sciences specifically.'
- 'Leigh Oliver is one of the practice’s leading stars with an enviable life sciences and healthcare client portfolio.'
Key clients
- Abu Dhabi National Oil Company
- Arch Capital Group
- Array Digital Infrastructure, Inc. (rebranded name of UScellular)
- Charter Communications, Inc.
- Davidson Kempner
- ED&F Man Commodities LTD
- Eni SpA
- GE Aerospace (rebranded name of General Electric Company)
- GE Vernova, Inc. (formerly part of General Electric Company)
- Hearst Corporation
- Informa PLC
- Intermediate Capital Group
- Keymed Biosciences Inc.
- LEONI AG
- Merck & Co., Inc.
- OMV AG
- Onex
- Partners Group
- Permira
- PIERER Mobility AG
Work highlights
Advised mobile network operating company United States Cellular Corporation (UScellular) and Telephone and Data Systems, Inc. on antitrust aspects of its US$4.4 billion sale to T-Mobile.
Advising on the antitrust regulatory clearance of Charter Communications, Inc.’s acquisition of Cox Communications, Inc., a strategic transaction valued at US $34.5 billion.
Advising multinational oil and gas company OMV AG on its agreement with Abu Dhabi National Oil Company (ADNOC) to combine Borouge plc and Borealis AG to form Borouge Group International, and on Borouge Group’s acquisition of Nova Chemicals for US$13.4 billion, establishing the world’s fourth-largest producer of polyolefins.
Practice head
Leigh Oliver; Joseph Ostoyich
Other key lawyers
Sharis Pozen; Michael Van Arsdall; Jonathan Elsasser; Lauren Rackow