On Thursday the Home Office announced the return of the blue British passport, to a chorus of approval from Brexiter newspapers and politicians. The irony is that the UK could have had a blue passport while an EU member. EU member state Croatia currently has a blue passport, after all. In any case – the “iconic” blue passport was imposed from abroad back in 1920 – thanks to the the League of Nations.

The EU never mandated burgundy passports: it simply produced a standard format that many member states chose to use for the sake of convenience. I imagine that the then UK government assumed that nobody cared that much about the colour of passports. It’s now clear that apparently trivial symbols of national identity are very meaningful for a lot of people. We’ll never know whether, had the government reintroduced blue passports when complaints first arose, the expense and disruption of Brexit could have been avoided.

After Brexit we will still have to follow the ICAO standard and US demands if our passports are to be recognised abroad

Passports also make an interesting case study on sovereignty, the concept so dear to Brexiters. Passports illustrate the limits of sovereignty in an interconnected world. As a sovereign state after Brexit, the UK will have the right to design passports in whatever way it chooses. But other states also have sovereignty: they have the sovereign right to decide which passports they accept for entry into their territory. The modern passport, since its introduction in the early 20th century, has always been a matter for negotiation between sovereign states. Transnational institutions and superpowers have often imposed requirements on supposedly sovereign states.

The Eurosceptic media used to complain about the size of British passports: the burgundy passports issued in the past few decades were smaller than the old blue ones. They have gone quiet about this recently, perhaps because they know that this isn’t something the UK can change after Brexit. Passport size, along with several other features, is mandated by the International Civil Aviation Organization (ICAO), an agency of the UN. Today’s passports are machine-readable, and an international standard is required so that all passports will fit the machines used in airports.

Most of the recent changes to British passports have been driven by the US rather than the EU. The US requires certain passport features for participation in its visa-waiver programme, which allows citizens of most developed countries to enter the US for business or recreation trips of up to 90 days without a visa. The US demands compliance with ICAO standards, but it also imposes more stringent photo requirements and biometric features.

The new US requirements have been imposed on the UK via the EU: the US informed the EU of its demands, and the EU then incorporated them into its own passport standards. But the UK would only be able to escape these requirements after Brexit by giving up visa-free travel to the US.

Regardless, those blue British passports so beloved of Brexiters had a design imposed by an international organisation. Prior to 1920, British passports consisted of a single sheet of card. In 1920, the League of Nations organised the Conference on Passports, Customs Formalities and Through Tickets in Paris. The resolution of this conference, passed on 21 October 1920, imposed a new set of standards that passports would have to meet to be internationally recognised.

British passports will be navy blue after Brexit, says Home Office Read more

The League of Nations ruling required that the passport be a booklet of 32 pages, with the dimensions 15.5cm x 10.5cm. It specified the information that the passport must contain, and the format it should be presented in. And it demanded that all passports be written in French, in addition to the national language of the issuing state. Today, ICAO standards require that passports must provide the information in English, French or Spanish. However, they specify that when the national language of the issuing state is English, French or Spanish, the passport should use one of the other two languages as well. After Brexit, the UK could decide to switch the second language of our passports from French to Spanish, but it could not eliminate the second language altogether, notwithstanding the fact that English is now the global lingua franca.

After Brexit we will still have to follow ICAO standards and US demands if our passports are to be recognised abroad. And, of course, we will still have to follow any new requirements that the EU may adopt, if we are to travel to our nearest neighbours.

After Brexit, the UK is determined to secure easy travel to the EU for UK citizens. There will be loud complaints from UK citizens, including Brexiters, if travel to our favourite holiday destinations in France and Spain becomes more difficult. It may be hard, if not impossible, to impose more stringent requirements on the ID cards that EU citizens use to travel to the UK, as the Home Office would like. And the UK will have lost its influence over EU measures to improve ID card security, which have made considerable progress in the past few years. Yet again, we may not be able to have our cake and eat it.

• James E Baldwin teaches history at Royal Holloway, University of London