Auckland professor’s tax research up for top international award

As the Trump administration prioritises domestic interests over multilateral agreements, a University of Auckland legal scholar warns of a “quiet revolution” reshaping international tax law.

Professor Craig Elliffe’s research on this shift is in the running for the 2025 Frans Vanistendael Award for International Tax Law, one of the field’s most prestigious honours. Published in the World Tax Journal, his paper, one of just six shortlisted for the €10,000 prize, explores how governments are strengthening domestic tax laws to combat tax avoidance, sometimes at the cost of weakening international agreements.

Elliffe looks at the relationship between international tax law, mainly tax treaties, and domestic tax law, examining how they interact and influence each other.

For decades, tax treaties have been the backbone of cross-border taxation, designed primarily to prevent double taxation - where the same income is taxed in two different countries. Over time, tax treaties have also been used to prevent tax avoidance and evasion, especially by multinational companies and wealthy individuals.

Elliffe argues that domestic law has prevailed against the more specialised law of tax treaties and at an increasing rate. This evolution has occurred in situations where the special law of treaties is “watered down” by the principle that treaties shouldn’t be allowed to be abused, or in situations where they facilitate tax avoidance.

"There's been a clear trend towards preserving and increasing the authority of certain domestic tax laws,” says Elliffe.

“There are many reasons for this reassertion of sovereign taxing rights, but they're mainly justified under the banner of preventing tax avoidance. Such domestic laws, however, can conflict with the reduction or elimination of double taxation and undermine the rationale for tax treaties."

Over the past decade, Elliffe says the pace of this trend has increased, suggesting more of a revolution than an evolution: a clear move towards preserving the authority of certain domestic tax laws.

"This means there's less certainty in law, which is a shame. It means countries can't rely on the treaties to the same extent they previously had.

"We're already seeing this kind of shift with the trade tariffs being imposed by the US; there’s this sort of breakdown of the existing cooperative global world trade and tax systems."

His paper raises questions about the future of international tax cooperation. If countries continue to prioritise domestic tax sovereignty over treaty commitments, he says the result may be a more fragmented and unpredictable tax landscape.