fanfan18
I don't think you read the article.
This part is the key part:
In leaving the EU, though, we drop out of something else, the nature of which is rarely discussed, mainly because it is so much of the fabric of our membership that it has been lost in the mists of time. The thing we lose is our membership of the Passport Union agreed at the European Council of December 1974 - shortly after we had joined the EEC.
This was implemented by the non-binding Council Resolution of 23 June 1981 and updated by the Council Resolution of 10 July 1995 which establish a uniform format for the passports of Member States.
When we drop out of the EU, therefore, it isn't just the Customs Union that goes. It is also the Passport Union. We become citizens of a "third country", reliant now on so-called Paris Conference on Passports and Customs Controls for the basis of document recognition. But, while that establishes uniform standards for international passports, it does not remove from individual states the right to set their own conditions for which documents they recognise.
In EU terms, to facilitate the entry of third country citizens to the EU, the passport issuing countries must appear on a permitted list, currently established by Decision No 1105/2011/EU, with a list of the recognised documents in respect of each country. Details can be accessed through a dedicated Council Website. An example of the actual list here, with the Schengen list here. The list is routinely updated by a Commission Implementing decision.
For a person from a third country to be able to enter the European Union without complications, the country that issued their travel documents must appear on this list. As Decision 1105/2011 helpfully states, "a Member State's failure to notify its position with regard to a travel document may cause problems to holders of that travel document".
The list itself records the individual permissions from the Member States and documents that are recognised – with the relevant conditions. If a country is not on this list, there is no validated evidence that any entry documents are valid – hence the likelihood of there being "problems".
Currently, the UK is not on that list. It cannot be because it is not a "third country". As long as it is in the EU, it is covered by a similar list available for download from the Council website which identifies EU Member States (and the Efta Members, which include Switzerland). But, from midnight of the 29 March 2019, the UK no longer qualifies to be on that list.
Whether the "third country" list will be updated immediately I simply do not know. But, since the list comprises the summation of the decisions made by the individual Member States as to what they will and will not accept, each state will have to make its own decisions and convey them to the Commission. The Commission will have to amend the list, showing the UK as a third country, with all the relevant details.
The point is that we are currently covered as an EU member state and after we leave the EU we will become a third country and will need to be treated as such.
This is not something which should be very difficult to do. It should be easier to fix than the aviation issue, for example. The problem is, if we leave the EU with no deal our situation will immediately change and we will be in a period of limbo until the issue is fixed. That could indeed mean that UK citizens are not able to use their UK passports to travel to an EEA country in the interim.
I live in France. It may be that the French border police would not allow me to use my UK passport to leave France during that period of limbo, in which case I would be stuck here. It may be that the French border police would allow me to leave France and the UK border police would allow me to enter the UK using my UK passport, but I could then find myself unable to re-enter France - where I live - until the situation is resolved.
So if I am in France and I am temporarily unable to use my passport to travel, if there is a family emergency at home in the UK, I could be stuck.