Aaron L. Nielson

Partner Litigation

Austin +1 512 355 4468

Overview

Aaron Nielson is a litigation partner in the Austin office of Kirkland & Ellis LLP, where he focuses on litigation in the U.S. Supreme Court and in other state and federal appellate courts. As a former Solicitor General of Texas, Aaron has deep experience with challenging agency rules, First Amendment litigation and preemption, and has personally argued a half dozen appeals in the U.S. Supreme Court. While serving as Texas Solicitor General, Aaron argued more than a dozen of the State of Texas’ most important appeals, oversaw all appellate litigation for the state, regularly provided solicited briefing to the Texas Supreme Court, and was a close advisor to the Attorney General as member of the Attorney General’s Executive Team.

Aaron is an elected member of the American Law Institute and a Senior Fellow of the Administrative Conference of the United States. He also co-chairs the American Bar Association Section of Administrative Law & Regulatory Practice’s Antitrust & Trade Regulation Committee. He is also a Professor of Law at the University of Texas.

Earlier in his career, Aaron served as a clerk to Justice Samuel A. Alito Jr. of the U.S. Supreme Court, Judge Janice Rodgers Brown of the U.S. Court of Appeals for the D.C. Circuit and Judge E. Smith of the U.S. Court of Appeals for the Fifth Circuit.

Administrative Law and Statutory Appeals

  • Rivers v. Guerro, 605 U.S. __ (2025): obtained unanimous U.S. Supreme Court decision barring successive attacks on state judgments.*
  • Wilson v. Midland County, 92 F.4th 1150 (5th Cir. 2024) (en banc): obtained en banc ruling adopting Texas’s view of complex federal statutory scheme.*
  • United States v. North, 985 F.3d 196 (3d Cir. 2021): helped persuade court to reverse criminal convictions of bank executive indicted for securities violations.

Constitutional Appeals

  • Free Speech Coalition v. Paxton, 605 U.S. __ (2025): persuaded U.S. Supreme Court to uphold Texas law requiring online pornography websites to age verify.*
  • Moody v. NetChoice, LLC, 144 S. Ct. 2383 (2024): litigated facial challenge to social media regulation.*
  • DeVillier v. Texas, 144 S. Ct. 938 (2024): persuaded U.S. Supreme Court to unanimously hold that plaintiffs alleging federal takings claims must use available state causes of action.*
  • Collins v. Yellen, 141 S. CT 1761 (2021): appointed by U.S. Supreme Court to brief and argue in defense of an act of Congress.*

Multidistrict Litigation

  • Street v. BP Exploration & Production, Inc., 85 F.4th 266 (5th Cir. 2023): part of team that persuade Fifth Circuit to affirm summary judgment in 40 consolidated toxic-tort appeals for lack of general causation.
  • In re Deepwater Horizon BELO Cases, 2022 WL 104243 (11th Cir. 2022): part of team that persuaded Eleventh Circuit to affirm exclusion of expert evidence in toxic-tort cases.
  • BP Exploration & Production, Inc. v. Claimant ID 100246928, 775 F. App’x 144 (5th Cir. 2019): principal author of briefing that successfully barred professional sports franchise from obtaining settlement award.

*Matters completed outside of Kirkland

Solicitor General of Texas

Senior Fellow, Administrative Conference of the United States

Honorable Samuel A. Alito, Jr.Supreme Court of the United States

Honorable Janice Rogers BrownUnited States Court of Appeals for the District of Columbia Circuit

Honorable Jerry E. SmithUnited States Court of Appeals for the Fifth Circuit

More

Thought Leadership

Representative Scholarship

Saving Agency Adjudication, 106 Texas Law Review 1013 (2025) (with Christopher Walker and Melissa Wasserman)

Article II and the Federal Reserve, 109 Cornell Law Review 843 (2024) (with Aditya Bamzai)

It’s Time for Congress to Set Internet Policy, Bloomberg News (April 2022)

Gaming Certiorari, 170 University of Pennsylvania Law Review (2022) (with Paul Stancil)

Deconstruction, Not Destruction, Daedalus: The Journal of the American Academy of Arts & Sciences (2021)

The Minor Questions Doctrine, 169 University of Pennsylvania Law Review 1181 (2021)

Three Wrong Turns in Agency Adjudication, 28 George Mason Law Review 657 (2021)

How Agencies Choose Whether to Enforce the Law: A Preliminary Investigation, 93 Notre Dame Law Review 1517 (2018)

Sticky Regulations, 85 University of Chicago Law Review 85 (2018)

Chevron Step One-and-a-Half, 84 University of Chicago Law Review 757 (2017) (with Daniel Hemel)

Confessions of an “Anti-Administrativist,” 131 Harvard Law Review Forum 1 (2017) (solicited response to Harvard Law Review Foreword)

Beyond Seminole Rock, 105 Georgetown Law Journal 943 (2017)

Memberships & Affiliations

Elected Member, American Law Institute

Co-Chair, Trade & Regulation Committee, American Bar Association’s Section of Administrative Law & Regulatory Practice

Credentials

Admissions & Qualifications

  • 2024Texas
  • 2016Utah
  • 2010District of Columbia

Courts

  • Supreme Court of the United States
  • United States Court of Appeals for the Fourth Circuit
  • United States Court of Appeals for the Fifth Circuit
  • United States Court of Appeals for the Sixth Circuit
  • United States Court of Appeals for the Federal Circuit
  • United States Court of Appeals for the District of Columbia Circuit
  • United States District Court for the District of Columbia

Education

  • Harvard Law SchoolJ.D.magna cum laude2007
  • University of CambridgeLL.M.2006
  • University of PennsylvaniaB.A.summa cum laude2003