The backstop and Article 62 of the Vienna Convention on the Law of Treaties

International law and Geoffrey Cox QC MP, the UK Government's Attorney General, burst onto centre stage this week as both became central to the UK Government's ongoing attempts to get its Brexit deal through the House of Commons.

On Tuesday (12 March), the Attorney General's legal opinion concluded:

• that the legal risk of the UK remaining permanently trapped in the backstop "remains unchanged” to the extent that this occurred "simply because of intractable differences" between the EU and UK on the efficacy of any proposed alternatives to the backstop;

although:

• he did consider that the "binding provisions" of both the Joint Statement by the UK and EU and the content of the UK's Unilateral Declaration "reduce the risk that the United Kingdom could be indefinitely and involuntarily detained within the [backstop's] provisions at least in so far as that situation had been brought about by the bad faith or want of best endeavours of the EU".

That the Attorney General did not feel able to go further, in regard to the first point above, in his advice was seen by many as a key contributor to the overwhelming rejection of the deal in the House of Commons the same day.

Since that defeat, it has been reported that the Attorney General is in discussions with the Democratic Unionist party and pro-Brexit Conservatives about whether the UK could use Article 62 of the Vienna Convention on the Law of Treaties unilaterally to pull out of the backstop at some future point and whether he may amend his advice to reflect this.

In fact, his advice on Tuesday already alluded to the point in the key paragraph in which he stated that the legal risk remains unchanged in relation to "intractable differences" as it states that in such circumstances "at least while the fundamental circumstances remained the same" there would be "no internationally lawful means of exiting the Protocol’s arrangements, save by agreement". Fundamental change of circumstances is the subject of Article 62.

In his answers to questions raised after his Statement to the House of Commons about his legal opinion the Attorney General referenced Article 62 and stated that it was "extremely important to remember that there is always a right to terminate a treaty unilaterally if circumstances fundamentally change … no question but that we have a right to exit if those circumstances apply."

So how likely are those circumstances to apply?

In addition to the requirement for circumstances to "fundamentally change", Article 62 has a number of other hurdles before it could be used unilaterally to withdraw from (or suspend the operation of) a treaty. The other key hurdles relevant to the backstop are that the:

• fundamental change must be one that "was not foreseen by the parties" at the time the treaty was entered into;
• circumstances which were subject to the fundamental change must have "constituted an essential basis of the consent of the parties to be bound by the treaty" in the first place; and
• effect of the fundamental change must have been "radically to transform the extent of obligations still to be performed under the treaty".

The first hurdle above on foreseeability puts those trying to think of circumstances where Article 62 might apply to the backstop into something of a catch-22. Indeed, the fact the UK and EU have been specifically talking about the circumstances in which the backstop may be terminated, but are not reaching any agreement to include explicit termination provision, must make it harder to sustain an Article 62 argument in the future. It is an open question as to whether recent efforts by the UK Government, by failing to achieve decisive changes to the text, might have made the UK's future position weaker as regards Article 62 (even if the UK's position may have been strengthened in other respects).

The Protocol on Northern Ireland states that the objective of the Withdrawal Agreement is "not to establish a permanent relationship between the Union and the UK", on which basis one might argue that circumstances leading to a permanent backstop would be fundamentally different from those anticipated by the parties.  However, there may be a difference between failing to reach an agreed negotiating objective (the risk of which might be said to have been implicit), and a fundamental change of circumstances arising from matters which could not possibly have been foreseen.

In any event, taken together, the hurdles are formidable. The main case law on Article 62 is from the 1997 International Court of Justice (ICJ) case between Hungary and Slovakia relating to a dispute over a communist-era project to build a hydroelectric power system on the Danube River (the Gabčíkovo-Nagymaros Project). Amongst the circumstances that Hungary identified as having fundamentally changed was the "socialist integration" for which the Treaty had originally been a "vehicle" and which had been overturned by the fall of the Soviet Union and the emergence of market economies in both states (not to mention the split of one of the signatories, Czechoslovakia, into the Czech Republic and Slovakia). In its judgment the ICJ did not consider that any of Hungary's arguments, individually or cumulatively, were sufficient as grounds under Article 62 to terminate the treaty. The ICJ was clear that "the stability of treaty relations requires that the plea of fundamental change of circumstances be applied only in exceptional cases" and also use the words "completely unforeseen" (our underlining).

In conclusion, it is difficult to foresee how Article 62 could be used by the UK in the future to walk away from the backstop. Although, as we note above, for the UK to succeed in any such claim it is likely vital that it cannot be foreseen…

For another possible approach to challenging the backstop see our View from Brussels note: Using EU law to improve the Brexit deal along the lines requested by the UK Parliament.