Ruth Mason

  • Class of 1957 Research Professor of Law

Ruth Mason joined the University of Virginia School of Law faculty in the 2013 fall semester as a professor of law. Prior to joining the Law School, Mason was the Anthony J. Smits Professor of Global Commerce at the University of Connecticut School of Law.

Mason has also been a visiting professor at Johannes Kepler University, Leiden University, Université Paris 1 (Panthéon Sorbonne), and Yale Law School. She served as a Fulbright Senior Scholar at the Vienna Institute for Austrian and International Tax Law in the winter of 2009. Mason was National Reporter for the United States to the 2008 International Fiscal Association (IFA) Congress on tax discrimination and to the 2014 European Association of Tax Law Professors Congress on tax information exchange. She is co-editor (with Ekkehart Reimer of the University of Heidelberg) of Kluwer's Series on International Taxation, and she is a member of the editorial board of the World Tax Journal.

Mason's research focuses on international, comparative, and state taxation. Her recent scholarship focuses on how tax nondiscrimination laws affect cross-border commerce in common markets.

Prior to joining the University of Connecticut, Mason was deputy director of the International Tax Program and executive director of the Graduate Tax Program at New York University School of Law. Before that, she was a tax associate in the New York office of Willkie Farr & Gallagher.

She received her undergraduate degree in U.S. history from Columbia University and her law degree from Harvard Law School.

Professor Ruth Mason Scores Victory for Taxpayers with Influential Supreme Court Amicus


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


Primer on Direct Taxation in the European Union (Thomson West, 2005). 

Selected Articles:

"Dual Residents: A Sur-Reply to Zelinsky" (with Michael Knoll), State Tax Notes 269 (2018).

Multi-part Special Report on EU state aid:

Part 1: "FAQ," 154 Tax Notes 451 (2017). 

Part 2: "Legitimate Expectations," 154 Tax Notes 615 (2017).

Part 3: "Apple," 154 Tax Notes 735 (2017).

Part 4: "Whose Arm’s Length Standard?," 155 Tax Notes 947 (2017).

Part 5: "An American View of State Aid," 157 Tax Notes 645 (2017).

"The Economic Foundation of the Dormant Commerce Clause" (with Michael S. Knoll),102 Va. L. Rev. 309 (2017).

“Is the Philadelphia Wage Tax Unconstitutional? And If It Is, What Can and Should the City Do?” (with Michael S. Knoll), 164 U. Pa. L. Rev. Online 163 (2016).
HeinOnline (PDF)

"Citizenship Taxation," 89 S. Cal. L. Rev. 169 (2016).
SSRN | HeinOnline (PDF)

“Shitizunshippu Kazei,” 66 Okayama L.J. 658 (2016).

Comptroller v. Wynne: Internal Consistency, a National Marketplace, and Limits on State Sovereignty to Tax” (with Michael S. Knoll), 163 U. Pa. L. Rev. Online 267 (2015).
HeinOnline (PDF)

“How the Massachusetts Supreme Judicial Court Should Apply Wynne” (with Michael S. Knoll), 78 State Tax Notes 921 (2015).

Wynne: It’s Not About Double Taxation” (with Michael S. Knoll), 75 State Tax Notes 413 (2015).

"Waiting for Perseus: A Sur-Reply to Professors Graetz and Warren" (with M. Knoll), 67 Tax L. Rev. 375 (2014).

"Delegating Up: State Conformity with the Federal Tax Base," 62 Duke L.J. 1267 (2013). 
SSRN | HeinOnline (PDF) 

"What Is Tax Discrimination?" (with Michael Knoll), 121 Yale L.J. 1014 (2012). 
SSRN | HeinOnline (PDF)

"Federalism and the Taxing Power," 99 Cal. L. Rev. 975 (2011). 

"Tax Expenditures and Global Labor Mobility, 84 N.Y.U. L. Rev. 1542 (2009). 

"Constitutional Restraints on Corporate Tax Integration" (with Walter Hellerstein and Georg Kofler), 61 Tax L. Rev. 1 (2009). 

"Made in America for European Tax: The Internal Consistency Test," 49 B.C. L. Rev. 1277 (2008) (quoted in Comptroller v. Wynne, 135 S. Ct. 1787, 1802 (2015)). 

"Flunking the ECJ’s Tax Discrimination Test," 46 Colum. J. Transnat’l L. 72 (2007).