Mark C. Williams

Corporate & Securities, Global Energy, Projects & Infrastructure

“‘Mayer Brown’s electric regulatory practice is unique as it has one of the foremost practitioners in the space – in Mark Williams – and is well suited to providing clients with a level of sophistication to their deal and transactional support that not too many legal platforms currently offer.’ ‘There are few firms I would place above Mayer Brown in providing regulatory transactional support for transactions and activities that require FERC approval. They are a go-to firm in this area.’”
Legal 500 US

Visión general

Mark Williams represents clients that invest in the electric power and natural gas industries. He has advised private equity funds, insurance-sector investors, banks, pension funds, multinational institutional investors, hedge funds, and traditional investment funds on the complex regulatory requirements applicable to electricity and gas investments. He also advises on electricity and gas investments, financings, mergers, acquisitions, securities, and restructuring transactions.


Mark serves or has served as:

  • Energy regulatory counsel to Ares EIF Management LLC, the manager of leading electricity and gas private equity funds.
  • Energy regulatory counsel to Global Atlantic Financial Group and its portfolio of generating companies.
  • Energy regulatory counsel to Astoria Energy project companies in New York.
  • Energy regulatory counsel to financial and institutional creditors and noteholders of over 50 generating companies and holding companies, in connection with workout and restructuring matters.
  • Lead regulatory counsel to General Electric Energy Financial Services in connection with the financing, development, and regulation of new clean-energy wind-generation facilities across the country.
  • Lead regulatory counsel to AIG Highstar Capital in its 2002 acquisition of the 6,000-mile Southern Star Central gas pipeline (and to Southern Star in its 2003 refinancing, to AIG and Southern Star in the 2005 acquisition by General Electric Capital, and to Southern Star in its 2006 refinancing).


  • Highly Regarded, IFLR1000 Financial and Corporate
  • Ranked, Energy: Electricity (Regulatory & Litigation) – USA, Chambers Global
  • Recommended, The Legal 500 US
  • Recognized, Project Finance Law, Washington, DC, The Best Lawyers in America
  • Ranked, Energy: Electricity (Regulatory & Litigation), Nationwide, Chambers USA
  • Highly Regarded, IFLR1000 United States
  • Leading Lawyer, IFLR1000 Financial and Corporate
  • Educación

    • Columbia University, BA
    • New York Law School, JD


    • District of Columbia
    • Nueva York


    • US Court of Appeals for the District of Columbia Circuit

    Participación Profesional y Comunitaria

    • Energy Bar Association: Vice Chair (2008–2010) and Chair (2010–2011) Committee on Professional Development and Ethics; Vice Chair, Chair-elect, and Chair, Committee on Finance and Transactions (2005–2007); Co-chair, Programs and Meetings Committee (2005–2006); Conference Chair, National Legislative Program (2005); Elected Member, Board of Directors (2002–2005); Founding Chair, Committee on Finance and Transactions (1999–2000); Chair, Committee on FERC Administration and Reorganization (1998–1999)
    • Trustee, Foundation of the Energy Law Journal (2011–2014)
    • Commissioner, City Industrial Development and Revenue Bond Authority, City of Alexandria, VA (Term 2002–2020; Chairman, 2012–2020)
    • Member, American Bar Association
    • Adviser to US Congress, House of Representatives, Subcommittee on Regulatory Reform and Paperwork Reduction (105th Congress) in connection with national electric-sector oversight hearings (1998)