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. Mason's research focuses on international, comparative, and state taxation. Her scholarship, which has been cited by the Supreme Court, focuses on how tax nondiscrimination laws affect cross-border commerce in common markets. Mason teaches courses in international and comparative tax law, and she teaches the International Tax Practicum. 

Mason has been a visiting professor at Johannes Kepler University, Leiden University, Université Paris 1 (Panthéon Sorbonne), and Yale Law School. She will be the International Bureau of Fiscal Documentation professor-in-residence until May 2019. In 2009, Mason served as Fulbright Senior Scholar at the Vienna University for Business Economics and Business Administration (WU Wien). Mason has twice served as co-National Reporter for the United States to international tax conferences: in 2008 to International Fiscal Association (IFA) and in 2014 to the European Association of Tax Law Professors. She is co-editor of Kluwer's Series on International Taxation with Ekkehart Reimer of the University of Heidelberg, and she is a member of the editorial board of the World Tax Journal.

Prior to joining the Law School, Mason was the Anthony J. Smits Professor of Global Commerce at the University of Connecticut School of Law.  Prior to that, she worked in the Graduate Tax Program at NYU and was a tax associate in the New York office of Willkie Farr & Gallagher.   

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:

"Digital Battlefront in the Tax Wars," (with L. Parada) 92 Tax Notes Int'l. 1183 (2018).

"Implications of Wayfair," 46 Int’l Tax Rev. 810 (2018).

"When Are Tax Subsidies Illegal?" 69 Am. U. L. Rev. (forthcoming 2019).

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).

Part 6: State-Aid on Appeal, 158 Tax Notes 771 (2018).   

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

"Citizenship Taxation," 89 S. Cal. L. Rev. 169 (2016).

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

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

"What Is Tax Discrimination?" (with Michael S. Knoll), 121 Yale L.J. 1014 (2012). 

"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). 






Episode 3: Taxing Big Tech and the Future of International Tax

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