The idea of Scotland losing its EU membership against its will has understandably provoked plenty of anger. What is less clear – and a question the recent meeting of Nicola Sturgeon and Theresa May has done little to resolve – is what can concretely be done about it. The "simplest" option from the perspective of European law would be for Scotland to apply for EU membership as an independent state outside of the UK. Such an option, however, is far from simple. It raises the spectre not only of a divisive second independence referendum but one conducted under a cloud of uncertainty.

Scottish membership would have to be negotiated under the shadow of wider negotiations between the UK and the EU over the future of their relationship (and in the face of a possible Spanish veto). The practical minefields of accession coupled with the unattractive choice (for many Scots at least) of having to "choose between" their British and European identities, drives the search for other solutions.

One possible answer is to think more deeply about citizenship. The idea of a distinct form of EU citizenship has been with us for more than 20 years but began as a relatively innocuous idea. Individual Europeans carry EU citizenship only in so far as they are citizens of one of the EU’s member states. In this way, I am an EU citizen only when I am a national citizen: logically, therefore, if my state leaves the EU, my EU citizenship disappears. It is this type of logic that led Donald Tusk a few weeks ago to remark that Scotland’s EU membership was merely "a matter for the UK".

There is, though, another way of thinking about EU citizenship. The European Courts have, over the last 20 years, done much to transform EU citizenship into a separate category. In numerous cases, they have insisted that – while it is for member states to decide who may acquire EU nationality – they are not entirely free to remove or deprive EU citizenship rights once they are acquired. In particular, EU citizenship means EU nationals living abroad should not be discriminated against or lose rights to social security or other benefits they have gained in other countries when moving across borders. We already have a form of EU citizenship that sees EU citizenship as European ie a bond that connects individual citizens to the EU itself.

Taking this thinking further would imply de-coupling national and EU citizenship. De-coupling would allow UK nationals – be they from London, Scotland or any other part – to retain their European citizenship rights of free movement and non-discrimination in other EU states if they so wished, even in circumstances where their states left the EU. While the decision to grant EU citizenship would still rest with member states, the decision to withdraw it would rest with the individual EU citizen.

There are, of course, a wealth of objections to such a proposal. One central objection is that it flies in the face of one of the central messages of the referendum, which rejected the free movement of persons while embracing the free movement of capital. This focus on people – on making the EU a more citizen-oriented project – may be precisely, however, what makes the separation of EU and national citizenship appealing. The separation of EU and national citizenship would allow the political Union that is the UK to remain in place while still allowing those who feel and act European (eg by living and working in other EU states) to retain rights to which they are deeply attached.

This proposal would involve putting the freedom of people, rather than of goods and trade, at the centre of any post-Brexit negotiation, either between the EU and the UK, or within the UK itself. If European citizenship really is – as the EU Treaties tell us – "fundamental", no government should be able to bargain the rights it brings away, without the consent either of the individuals involved or the EU as a whole. This is, in short, no "internal" question, but one for which Europe as a whole is responsible.

Separating national and EU citizenship would be a radical step. It would involve complicated bargaining. In view of the range of unattractive options faced by the Scottish Government, it may be time, however, to think radically. A new form of citizenship may be one way of allowing Scots to avoid a fateful choice – between a British or a European future.

Daniel Augenstein is an associate professor at Tilburg Law School in the Netherlands. Mark Dawson is Professor of European Law and Governance at Hertie School of Governance, Berlin.