Lessons from International Law
International law does not regulate explicitly a matter like the loss of European citizenship for UK citizens, nor the loss of territorial EU citizenship rights for second country nationals in the UK. Some have argued that British expats in the Union would have ‘acquired rights’ under the 1969 Vienna Convention on the Law of Treaties (VCLT). Reference is to vested rights under Article 70(1)(b) VCLT and to the formula ‘(b) does not affect any right, obligation or legal situation of the parties created through the execution of the treaty prior to its termination.’ This source of international law is an unlikely candidate for protecting acquired rights.3 It is unclear, to say the least, if such a notion could be used in the first place; if it would cover the situation; if it would cover all rights; or else, which rights? whose rights? and with what exact practical impact? Retaining ‘executed’ rights - that is, those rights that are not automatically revoked if a treaty or law no longer applies, and that can be retained even in the event of a change in the ultimate power over a country - refers to ‘private’ rights, whereas EU citizens’ rights include highly ‘public’ rights, for example, voting and standing in elections at local and European level. Not much solace is to be found in this reference to international law.
The ban on arbitrary deprivation of citizenship recurrent in many international instruments - others venture - might have some bearing: As things currently stand, ‘questions are bound to arise, should the withdrawing state be willing to retroactively terminate the rights enjoyed by EU citizens connected with other member states in its own territory’ (Kochenov 2016). Yet, it would be limited to cases of retroactive restrictions and would therefore be silent on the situation of post-exit restrictions.
Can international law at least provide us with guidelines as to what happens to Union citizenship in the case at hand? If we look at how nationality matters have been regulated in state succession scenarios, some interpretative aids may be distilled. The analogical reasoning is warranted by the fact that the problems, which secessions pose to citizenship at the national level, are very similar to the problems posed by withdrawals from the EU in relation to Union citizenship (Closa 2014), even though there are limits to the analogy: The EU is not a state; it is difficult to argue for the existence of a change in sovereignty; no new nationality law needs to be written. Previous experiences cannot easily be made to fit Brexit, especially considering the emphasis of the European Court of Justice on Union citizenship being the fundamental status of nationals of member states.
There are three lessons to learn from the state succession literature as far as guiding principles are concerned: The leaving country and the remaining bloc have a duty to negotiate solutions, the leaving country has a duty to inform and possibly to suggest options for individuals concerned.