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Jack T. LeBris Erffmeyer is a member of the Energy & Natural Resources Practice in Greenberg Traurig’s Washington, D.C. office. As a former Assistant Attorney General for the Public Utilities Bureau in the Office of the Illinois Attorney General, Jack was responsible for the prosecution and management of all aspects of administrative litigation before the Illinois Commerce Commission (ICC) on electricity and natural gas cases and before the Federal Energy Regulatory Commission (FERC) on interstate wholesale electricity market cases. His experience includes casework related to formula rate update cases, traditional rate cases, and rider reconciliations, implicating issues such as prudence of capital expenditures, cost-allocation, novel rate designs, accumulated and excess deferred income tax regulatory accounting, statutory infrastructure upgrade programs, bad debt expense, return on equity, and ratemaking implications of the 2017 federal income tax law change.



  • Litigated as part of a three-attorney team a major RTO/ISO capacity market case before FERC on behalf of the People of the State of Illinois from initial protest of tariff filings, to initial and reply briefs and testimonies in a new contested proceeding, and two requests for rehearing.°
  • Coordinated with aligned parties and lead drafting of a protest to FERC for a group of consumer advocates in an RTO/ISO tariff filing proceeding seeking to dramatically modify the capacity market of a specific capacity zone within the grid operator’s territory.°

°The above representations were handled by Mr. LeBris Erffmeyer prior to his joining Greenberg Traurig, LLP.

  • Assistant Attorney General, Office of the Illinois Attorney General, Public Utilities Bureau, 2017-2019
  • Attorney and Policy Advocate, Citizens Utility Board, 2016-2017
    • Federal Energy Regulatory Commission,
  • Law Clerk, Office of Administrative Law Judges and Dispute Resolution, 2015-2016
  • Federal Energy Regulatory Commission
    • Law Clerk, Office of Administrative Litigation, 2014 and 2015
    • Summer Law Clerk, Office of Administrative Litigation, 2014
  • Legal Intern, U.S. Department of Energy, Office of the General Counsel, Electricity & Fossil Energy, 2014
  • Legal Fellow, American Wind Energy Association, 2014
  • Legal Intern, Northern Virginia Regional Commission, 2013

Recognition & Leadership

  • Member, Energy Bar Association, 2014-Present
  • Member, American Bar Association, 2015-2020
    • Member, Environment, Energy and Resources Law Group, 2015-2020


  • J.D., with honors, The George Washington University Law School
    • Senior Projects Editor, The George Washington Journal of Energy and Environmental Law
  • B.S., Environmental Geoscience, Boston College
  • Illinois
Admitted to practice in Illinois. Not admitted in the District of Columbia. Practice in D.C. supervised by shareholders admitted to practice in D.C. Practice limited to Federal Courts and Agencies.
  • French, Basic Conversation