As observers of global tax policy know, international tax issues are dealt with in bilateral treaties that more or less adhere to a 'model' tax treaty developed and periodically updated by the OECD (provisions in a rival UN Model are occasionally invoked, and the US has its own model with its own distinctions and idiosyncrasies). There are those who have long lamented the problem of having thousands of bilateral agreements that can't be easily or quickly updated when the OECD revises the model (thus curbing the impact of OECD soft law).
As part of the base erosion and profit shifting (BEPS) initiative, the OECD is currently developing a
"Multilateral instrument on tax treaty measures to tackle BEPS" which would be used to 'modify' all existing tax treaties in force among signatory countries. The OECD says this mechanism (which it calls an 'innovative approach') 'would preserve the bilateral nature of tax treaties' even as it modified all existing bilateral treaties 'in a synchronized way'. The OECD says there are "limited precedents" for modifying bilateral treaties with a multilateral instrument.
But are there really any precedents at all? I couldn't think of any off-hand. A quick check with a few international law colleagues yielded few comparators. Tim Meyer suggested the EU harmonizing efforts on Bilateral Investment Treaties (BITs) as a candidate, albeit noting that this does not contemplate directly overriding existing BITs but requires EU members to change their bilateral arrangements to conform with EU investment policy.
Tim also made the interesting observation that"treaties that reference customary international law standards, such as BITs’ reference to the minimum standard of treatment" could be overridden in a somewhat similar fashion. He explained that "[i]f custom changed, such as through the promulgation of soft law documents or multilateral treaties, it would change the BITs that incorporate the customary standard. That isn’t exactly the same thing [as the new OECD multilateral instrument], but similar."
The OECD's work in developing "global consensus" has in the past led some to describe OECD standards as "soft law" and others to suggest that the OECD may be understood to articulate customary international tax law; moreover the OECD has itself now taken to describing its model as soft law (including in its 2014 report on the multilateral instrument). I have urged caution in defining OECD proclamations as soft law or customary law given the OECD's exclusive membership of mainly rich countries, which excludes all of the BRICs and most of the rest of the world, as I think the nomenclature lends an imprimatur of legitimacy to OECD proclamations that may not be deserved. But it seems clear that the BEPS action items, and the new global forum to "monitor compliance" with them, are intended to overcome the exclusivity problem while endowing OECD norms with ever-greater law-like effect (without offending the unicorn that is "tax sovereignty").
It seems likely to me that a multilateral agreement that modifies existing tax treaties is actually intended to ultimately replace those treaties, making small and incremental modifications until the underlying bilateral treaties become superfluous or extinct. Accordingly I view the OECD's multilateral 'modification' function to be an exercise in creeping harmonization as well as "ossification" (or maybe transformation) of soft law into hard law.
Adding together the other elements of BEPS, including the new global forum to compel national compliance with 'minimum standards' as they develop, I recently suggested that the OECD's tax folks are giving birth to a new global tax order complete with rules, audits, and reform processes. This is perhaps not the order envisioned by those who have in the past called for global tax coordination in a supranational body for the sake of pursuing global tax justice. If the OECD-based regime is not fully supranational yet, it is close, and it looks increasingly inevitable once it sets a multilateral agreement in place.
There are many fascinating threads of soft law and public international law are at work in these developments. I recently came across an article by Jung-Hong Kim on the topic, entitled A New Age of Multilateralism in International Taxation?, abstract:
With the OECD/G20 BEPS project, the current international tax landscape is facing challenges and changes unprecedented for the past several decades. This paper looks at the development of bilateralism and multilateralism in the current international tax regime, takes stock of the BEPS works and analyzes the proposed Multilateral Instrument. Then, the paper discusses the emerging multilateral tax order in international taxation.
Historically, bilateralism has been the constant trend of tax treaties, and later multilateral tax treaties have emerged in some regional areas. There being some deficiencies with bilateral treaties such as dilapidation, delay in entry into force and vulnerability to treaty shopping, the experience of multilateral tax treaties can help build a foundation for future development of a multilateral tax treaty to complement the bilateral tax treaty network.
With a caveat that BEPS output is fluid at this stage, drawing on the various examples of existing non-tax multilateral treaties, the Multilateral Instrument will be a desirable and feasible tool to reflect the necessary changes resulting from BEPS project. For Korea whose tax treaties need a systematic upgrade after a noticeable growth in quantity, the negotiation on the Multilateral Instrument of the BEPS project will be a great opportunity to revisit the existing bilateral tax treaties and to make appropriate amendments with bilateral treaty partners in multilateral format.
Beyond BEPS, supposing that the work on the Multilateral Instrument results in a multilateral convention, the inevitable question is the emergence of a multilateral tax order. In terms of feasibility of such a multilateral tax order, there are both positive and negative sides. The positive side is that the relative success of Global Forum on Tax Transparency can be a guidance on the post-BEPS multilateral tax order. On the other hand, the phenomenon of diminishing multilateral trade regime and bilateral investment treaty regime seem to be a negative evidence. Another point to consider is the appropriate forum to manage the multilateral tax order. For this, there are two competing organizations, i.e., the OECD CFA and UN tax committee, each of which having some limit to be developed into an intergovernmental forum.
After all, the essential question will be how those major players such as the U.S., EU, China, India etc. could build a consensus by compromising on the institutional and substantive aspects of the multilateral tax order. For now, for the emerging multilateral tax order to proceed on a sound basis, the work of the BEPS project should bear substantive and meaningful fruits.