Ruth Mason

  • Edwin S. Cohen Distinguished Professor of Law and Taxation
  • Class of 1941 Research Professor of 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


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

Major Articles:

"The Transformation of International Tax," 114 Am. J. Int'l L. 353 (2020).
SSRN | Video

"Identifying Illegal Subsidies," 69 Am. U. L. Rev. 479 (2019).
SSRN | HeinOnline (PDF) |  Video

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

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

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

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

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

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

"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)). 
 | HeinOnline (PDF)

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

"U.S. Tax Treaty Policy and the European Court of Justice," 59 Tax L. Rev. 65 (2005).
Selected Other Work:

“The 2021 Compromise,” 172 Tax Notes Fed. 569 (2021).
SSRN | Tax Notes Video

"The Legality of Digital Services Taxes under EU Law" (with L. Parada), 40 Va. Tax Rev. 175 (2020). 
SSRN | Video

"The Dormant Foreign Commerce Clause After Wynne" (with M. Knoll), 39 Va. Tax Rev. 357 (2020). 
SSRN | HeinOnline (PDF)

"Company Size Matters" (with L. Parada), 2019 Brit. Tax Rev. 610 (2019). 
"Implications of Wayfair," 46 Intertax 810 (2018)
SSRN | Podcast
"Digital Battlefront in the Tax Wars" (with L. Parada), 92 Tax Notes Int’l 1183 (2018).
Multi-part Special Report on tax rulings as EU state aid: 

Part 1 — "State Aid FAQ," 154 Tax Notes 451 (2017).

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

Part 3 — "Apple," 154 Tax Notes 735 (2017). Common Law Podcast

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). Video

Part 6 — "State Aid: Arm’s Length on Appeal," 158 Tax Notes Fed. 771 (2018).

Part 7 — "Implications for Apple of Starbucks and Fiat," 154 Tax Notes Fed. 93 (2019).

Part 8 — "The General Court Decision in Apple" (with S. Daly), 168 Tax Notes Fed. 1791 (2020).  Tax Notes Podcast

Part 9 — "State Aid Enforcement After Amazon," 171 Tax Notes Fed. 1395 (2021).

"New Yorks Unconstitutional Tax Residence Rule" (with M. Knoll), 85 State Tax Notes 707 (2017).

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

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

"Exporting FATCA" (with J. Blank), 142 Tax Notes 1245 (2014).

"Tax Discrimination and Capital Neutrality", 2 World Tax J. 126 (2010). (invited contribution)

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

"Sovereign Wealth Funds and the Efficient Management of the Wealth of Nations," 120 Tax Notes 1321 (2008).

"Common Markets, Common Tax Problems," 8 Fla. Tax Rev. 599 (2007) (symposium).
SSRN | HeinOnline (PDF)

"Double Taxation: A European 'Switch in Time'?" (with G. Kofler), 14 Colum. J. Eur. L. 63 (2007).
SSRN| HeinOnline (PDF)

"When Tax Treaty Derivative Benefits Provisions Don’t Apply," 43 Tax Notes Int’l 563 (2006).



The Transformation of International Tax

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