Felicia H. Ellsworth


Ellsworth, Felicia H.

Felicia Ellsworth has built a distinguished portfolio of work in the Litigation/Controversy Practice Group as a member of both the Appellate & Supreme Court Litigation Group and Business Trial Group. Her trial practice focuses on high-stakes complex commercial litigation in both state and federal courts, and her appellate practice spans both civil and criminal matters in the state and federal appeals courts, including the Supreme Court of the United States.

Ms. Ellsworth has counseled numerous clients in commercial disputes on issues including patent infringement, trade secret misappropriation, contract law, civil procedure, real property disputes, tort law, administrative law and procedure, and constitutional law. She has also counseled and represented clients in both civil and criminal appeals involving patent infringement, contract law, constitutional law, and criminal law and procedure. Ms. Ellsworth has represented clients in Massachusetts and other state trial and appellate courts, including the Supreme Judicial Court, in administrative tribunals, as well as in federal district courts and in the United States Courts of Appeals for the First, Second, Fourth, Fifth, Sixth, Ninth, Tenth, and Federal Circuits, and the Supreme Court. She has argued before both federal and state appeals courts, including the First, Second, and Sixth Circuits and the Massachusetts Appeals Court.

Recent Highlights

  • Defending against putative class action lawsuits in federal and state court arising out of a recent highly publicized data breach. 
  • Representing multinational networking equipment manufacturer in a patent infringement appeal in the Federal Circuit and Supreme Court, in a case argued in the Supreme Court in March 2015. 
  • Helped lead the WilmerHale team in filing a brief in Obergefell v. Hodges, concerning government recognition of the freedom to marry, on behalf of a total of 303 Republican, libertarian, conservative and center-right high-profile activists and government officials, including past presidential candidates, seven current and former governors, and 23 current and former members of the House of Representatives and US Senate. The brief received significant media attention when filed.
  • Representing a private beverage company in the Ninth Circuit and Supreme Court in an important Lanham Act case, resulting in a unanimous ruling in the client's favor in a case that attracted significant press coverage, including in The New York Times and Law360.
  • Helped lead the WilmerHale team in filing amicus briefs on behalf of Gay & Lesbian Advocates & Defenders in the Fourth, Fifth, Sixth, Seventh, and Tenth Circuits in appeals arising out of challenges to same-sex marriages bans in several states. Ms. Ellsworth and the team have argued that these bans cannot survive rational-basis review because the proffered rationales for the ban either lack a rational connection to the bans or are based on illegitimate purposes, or both.
  • Representing a multi-national oil and gas company in several matters as part of a litigation in which tens of billions of dollars in damages are sought from energy industry companies based on allegations that oil and gas development work over many decades has damaged coast property in Louisiana and made it more vulnerable to flood damage.
  • Leading the WilmerHale team representing the State of Vermont in a matter involving the proposed relicensing of the Vermont Yankee Nuclear Power Station in administrative relicensing proceedings before the Vermont Public Service Board. The proceeding spanned approximately 18 months and culminated in a combined five weeks of hearings in 2013.
  • Representing a medical device manufacturer in a successful appeal to the Supreme Judicial Court of Massachusetts involving damages and injunctive relief.
  • Presented oral argument on behalf of appellee American Honda in W&D Imports Inc. v. Lia. Five days after oral argument, the panel issued a summary order affirming the decision in American Honda's favor. 
  • Ms. Ellsworth has filed numerous amicus curiae briefs in both in the Supreme Court, Federal Circuit and other courts of appeals addressing a variety of different topics. Most recently, Ms. Ellsworth filed an amicus brief in support of certiorari on behalf of a group of Internet industry companies in Spokeo Inc. v. Robins.    
  • Helped lead a team of WilmerHale lawyers that began representing the Commonwealth of Massachusetts in 2009 as co-counsel in its challenge to the constitutionality of DOMA, the first in the nation. Both the District of Massachusetts and the First Circuit struck down DOMA as unconstitutional—marking the first ruling by a federal appeals court striking down DOMA. These decisions were later confirmed by the Supreme Court's decision in United States v. Windsor. In the Windsor case, Ms. Ellsworth once again helped lead a WilmerHale team in filing an amicus brief on behalf of more than a dozen former Solicitors General of the United States, White House Counsel, and heads of the Office of Legal Counsel explaining that the Supreme Court has jurisdiction to hear a case challenging DOMA even though the federal government did not defend the law. The Court's jurisdictional ruling was essential to its ultimate decision to strike down DOMA.
  • Helped lead the WilmerHale team in filing a brief in Hollingsworth v. Perry, challenging the constitutionality of California's Proposition 8, on behalf of more than 100 prominent Republicans, including top advisers to former President George W. Bush, seven former governors, and 12 current and former members of Congress. The brief received significant media attention that included coverage by The Wall Street Journal, National Law Journal and Law360

Honors & Awards

  • Recognized as an "Up & Coming Lawyer" by Massachusetts Lawyers Weekly in its 2015 Excellence in the Law edition
  • Named a "Massachusetts Super Lawyers' 'Rising Star'" in 2015 in the area of Appellate and Supreme Court Litigation

Professional Activities

Ms. Ellsworth is admitted to practice in the Commonwealth of Massachusetts and before the United States District Court for the District of Massachusetts, the United States Courts of Appeals for the First, Second, Sixth, Tenth, and Federal Circuits, and the Supreme Court of the United States. She is also a member of the Boston Bar Association and the Women’s Bar Association.


Ms. Ellsworth served as a Special District Attorney in the Middlesex District Attorney's Office from November 2010-April 2011, where she prosecuted cases involving violent crimes, financial fraud, and many other offenses. Previously, Ms. Ellsworth served as a law clerk to Chief Justice John G. Roberts, Jr. of the Supreme Court of the United States, and then-Chief Judge Michael Boudin of the United States Court of Appeals for the First Circuit. During law school, Ms. Ellsworth served as editor-in-chief of The University of Chicago Law Review and interned with the United States Attorney's Office for the District of Massachusetts.

Publications & News


May 21, 2015

Felicia Ellsworth Recognized Among Massachusetts Lawyers Weekly Up & Coming Lawyers

Massachusetts Lawyers Weekly has recognized Partner Felicia Ellsworth in its 2015 Excellence in the Law edition.

March 8, 2015

Leading Boston Law Firms Join Forces to Challenge Public Charter School Cap, Ensure Students' Rights

In an unprecedented joint legal effort, three leading Boston law firms—WilmerHale, Goodwin Procter, and Foley Hoag—announced this morning that they plan to file a pro bono lawsuit on behalf of Boston school students to lift the state's cap on public charter schools and ensure every student's constitutional right to an adequate education.

March 6, 2015

303 Conservatives File Historic Amicus Brief in Marriage Equality Case Before US Supreme Court

Project Right Side and former RNC Chairman Ken Mehlman formally filed an amicus brief with the United States Supreme Court involving four landmark cases slated to be heard on April 28, 2015 concerning government recognition of the freedom to marry.

December 31, 2014

Direct-to-Consumer Wine Shipment Comes to Massachusetts on January 1

This holiday season brings an extra reason to celebrate for Massachusetts wine enthusiasts.

November 20, 2014

Prominent Lawyers Publish Essay Defining and Shaping Ethical Responsibilities of Lawyers

Harvard Law School's Center on the Legal Profession and Wilmer Cutler Pickering Hale and Dorr LLP are pleased to announce the publication of an essay calling for lawyers, as professionals and as citizens, to balance concerns about the current economic transformation of lawyering with a strong commitment to four ethical responsibilities: to clients/stakeholders, the legal system, their own institution and society. The essay is co-authored by three internationally renowned lawyers representing corporate, law firm and academic environments.

June 17, 2014

US Supreme Court Issues Unanimous Ruling in Favor of WilmerHale Client POM Wonderful

On June 12, 2014, the US Supreme Court ruled unanimously in favor of WilmerHale client POM Wonderful LLC (POM) in an important case involving the intersection of the Lanham Act’s prohibition on false advertising and the Federal Food, Drug, and Cosmetic Act's (FDCA) regulation of food and beverage labeling.

January 6, 2014

WilmerHale Announces the Elevation of Partners and Special Counsel

We are pleased to announce the elevation of our new partners and special counsel.

June 26, 2013

WilmerHale Plays Key Role in Historic Supreme Court Ruling Favoring Marriage Equality

On June 26, 2013, the Supreme Court of the United States issued two long-awaited decisions affecting the legality of same-sex marriage. The law firm WilmerHale played a significant role in both cases, which involved challenges to the federal Defense of Marriage Act (DOMA) and California’s Proposition 8.

June 1, 2012

First Circuit Holds DOMA Unconstitutional

April 27, 2010

WilmerHale Wins Fifth Case in the Federal Circuit in Two Weeks

Pro Bono and Community Involvement

Throughout her time at the firm, Ms. Ellsworth has become deeply involved in numerous pro bono matters. Recently and significantly, she played a lead role in the Commonwealth of Massachusetts' challenge to the constitutionality of DOMA, leading to the historic Supreme Court ruling favoring marriage equality.

Ms. Ellsworth remains involved in the fight for marriage equality nationwide, and is helping lead the firm's representation of Gay and Lesbian Advocates and Defenders in various federal courts of appeals considering marriage equality issues in the Fourth, Sixth, Seventh and Tenth Circuits.

In addition to her marriage equality pro bono representations, Ms. Ellsworth has a robust pro bono practice that includes representing individuals seeking asylum based on religious and gender persecutions and individuals appealing their criminal convictions and sentences. She is a member of the First Circuit Court of Appeals Criminal Justice Act panel, through which she provides pro bono representation to indigent defendants on appeal.


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JD, High Honors, University of Chicago Law School, 2005, Order of the Coif; Editor-in-Chief, The University of Chicago Law Review

BS, Foreign Service, cum laude, Georgetown University, School of Foreign Service, 2000, Honors Certificate in Muslim-Christian Understanding

Bar Admissions



The Hon. Michael Boudin, US Court of Appeals for the First Circuit, 2005 - 2006

The Hon. John G. Roberts, Jr., US Supreme Court, 2006 - 2007