Ruth Mason

  • Edwin S. Cohen Distinguished Professor of Law and Taxation
  • Class of 1941 Research Professor of Law
  • Director, Virginia Center for Tax Law

Ruth Mason joined the University of Virginia School of Law faculty in 2013. Her research focuses on taxation, especially issues related to cross-border taxation — including citizenship-based taxation and taxation within federations and common markets. Her recent work considers multilateral efforts to reform corporate taxation. Mason has an abiding interest in the dormant commerce clause and tax discrimination, and her work in this area has been cited by the U.S. Supreme Court.

Mason has been a visiting professor at Yale Law School and Université Paris 1 (Panthéon Sorbonne). She was a Fulbright senior scholar at Vienna University of Economics and Business. As professor-in-residence at the International Bureau of Fiscal Documentation in 2018, Mason delivered the 2018 Amsterdam Distinguished Lecture in Taxation. Her lecture focused on the application to U.S. multinational companies of the EU prohibition of tax state aid. She developed the lecture into a method that regulators could use to reliably identify subsidies delivered as tax breaks.

Mason co-edits Kluwer’s Series on International Taxation, and she is a member of the editorial board of the World Tax Journal. She also has served as national reporter for the United States to the International Fiscal Association. Prior to joining the Law School, Mason taught at New York University School of Law and University of Connecticut School of Law. She practiced at Willkie Farr & Gallagher in New York City.

Mason is actively involved in the life of the Law School and University. She supervises doctoral students, teaches taxation and serves as faculty adviser to UVA’s tax moot court team, which has won three international championships. Mason recently participated in an episode of UVA’s Global Inquirer and she co-hosts the Oxford-Virginia Legal Dialogs.



  • J.D.
    Harvard Law School
  • B.A.
    Columbia University

Highlighted Works

The Transformation of International Tax, 114 American Journal of International Law 353-402 (2020).

Identifying Illegal Subsidies, 69 American University Law Review 479-564 (2019).

The Economic Foundation of the Dormant Commerce Clause (with Michael S. Knoll), 103 Virginia Law Review 309-354 (2017).

Citizenship Taxation, 89 Southern California Law Review 169-239 (2016).

Delegating Up: State Conformity with the Federal Tax Base, 62 Duke Law Journal 1267-1348 (2013).

What is Tax Discrimination? (with Michael S. Knoll), 121 Yale Law Journal 1014-1117 (2012).

Federalism and the Taxing Power, 99 California Law Review 975-1036 (2011).

Tax Expenditures and Global Labor Mobility, 84 NYU Law Review 1540-1622 (2009).

Made in America for European Tax: The Internal Consistency Test, 49 Boston College Law Review 1277-1326 (2008).

Flunking the ECJ's Tax Discrimination Test, 46 Columbia Journal of Transnational Law 72-132 (2007).

U.S. Tax Treaty Policy and the European Court of Justice, 59 Tax Law Review 65-132 (2005).

Complete List of Works


Bibb Balancing (with Michael S. Knoll), George Washington Law Review (2023).


Thinker, Teacher, Traveler: Reimagining International Tax (edited with Georg Kofler, Alexander Rust), IBFD (2021).

Book Chapters

Tax Discrimination (with Elizabeth Adams & Michael Knoll), in Research Handbook on International Taxation, Edward Elgar, 44-63 (2020).

Articles & Reviews

Has Cross-Border Arbitrage Met Its Match? (with Pascal Saint-Amans), 41 Virginia Tax Review (2021).
The 2021 Compromise, 172 Tax Notes Federal 569 (2021).
Special Report on EU State Aid: Part 8—State Aid: The General Court Decision in Apple (with Stephen Daly), 168 Tax Notes Federal 1791-1806 (2020).
Steiner v. Utah: Designing a Constitutional Remedy (with Michael S. Knoll), 95 Tax Notes State 845-850 (2020).
The Dormant Foreign Commerce Clause After Wynne (with Michael S. Knoll), 39 Virginia Tax Review 357-418 (2020).
The Legality of Digital Taxes in Europe (with Leopoldo Parada), 40 Virginia Tax Review 175-217 (2020).
The Transformation of International Tax, 114 American Journal of International Law 353-402 (2020).
Why the Supreme Court Should Grant Certiorari in Steiner v. Utah (with Michael S. Knoll), 95 Tax Notes State 377-388 (2020).
Company Size Matters (with Leopoldo Parada), 2019 British Tax Review 610-650 (2019).
Identifying Illegal Subsidies, 69 American University Law Review 479-564 (2019).
Digital Battlefront in the Tax Wars (with Leopoldo Parada), 92 Tax Notes International 1183-1197 (2018).
Dual Residents: A Sur-Reply to Zelinsky, 158 Tax Notes 269-272 (2018).
Implications of Wayfair, 46 Intertax 810-819 (2018).
New York’s Unconstitutional Tax Residence Rule (with Michael S. Knoll), 85 State Tax Notes 707-716 (2017).
Special Report on EU State Aid: Part 1—FAQ, 154 Tax Notes 451-462 (2017).
Special Report on EU State Aid: Part 3—Apple, 154 Tax Notes 735-751 (2017).
The Economic Foundation of the Dormant Commerce Clause (with Michael S. Knoll), 103 Virginia Law Review 309-354 (2017).
Citizenship Taxation, 89 Southern California Law Review 169-239 (2016).
Is the Philadelphia Wage Tax Unconstitutional? And If It Is, What Can and Should the City Do?, 164 University of Pennsylvania Law Review Online 163-178 (2016).
Comptroller v. Wynne: Internal Consistency, a National Marketplace, and Limits on State Sovereignty to Tax (with Michael S. Knoll), 163 University of Pennsylvania Law Review Online 267-283 (2015).
How the Massachusetts Supreme Judicial Court Should Apply Wynne (with Michael S. Knoll), 78 State Tax Notes 921-928 (2015).
Wynne: It’s Not About Double Taxation (with Michael S. Knoll), 75 State Tax Notes 413-422 (2015).
Exporting FATCA (with Joshua D. Blank), 142 Tax Notes 1245-1250 (2014).
Waiting for Perseus: A Sur-Reply to Professors Graetz and Warren (with Michael S. Knoll), 67 Tax Law Review 375-452 (2014).
Delegating Up: State Conformity with the Federal Tax Base, 62 Duke Law Journal 1267-1348 (2013).
What is Tax Discrimination? (with Michael S. Knoll), 121 Yale Law Journal 1014-1117 (2012).
The Constitutional Limits of Taxing and Spending, 38 Administive & Regulatory Law News 2-3, 12 (2012).
Federalism and the Taxing Power, 99 California Law Review 975-1036 (2011).
Tax Discrimination and Capital Neutrality, 2 World Tax Journal 126 (2010).
Tax Expenditures and Global Labor Mobility, 84 NYU Law Review 1540-1622 (2009).
Made in America for European Tax: The Internal Consistency Test, 49 Boston College Law Review 1277-1326 (2008).
Constitutional Restraints on Corporate Tax Integration (with Walter Hellerstein & Georg W. Kofler), 62 Tax Law Review 1-66 (2008).
Double Taxation: A European "Switch in Time"? (with Georg W. Kofler), 14 Columbia Journal of European Law 63-98 (2007).
Flunking the ECJ's Tax Discrimination Test, 46 Columbia Journal of Transnational Law 72-132 (2007).
Common Markets, Common Tax Problems, 8 Florida Tax Review 599-628 (2007).
When Tax Treaty Derivative Benefits Provisions Don’t Apply, 43 Tax Notes International 563-567 (2006).

Op-Eds, Blogs, Shorter Works

Is the Biggest Supreme Court Case This Term About Bacon? (with Michael S. Knoll), The Regulatory Review (November 14, 2022).
The Time Has Come for State Digital Taxes (with Darien Shanske), Daily Tax Report (May 29, 2020).
What the States Need from Congress Now Is Cold, Hard Cash (with Daniel Hemel & Gladriel Shobe), Time (April 14, 2020).




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