I assume youre refering to this bit in that article usuallydormant?
"Most people will no doubt continue to move freely across the border, but the CTA applies only to British and Irish citizens."
Tut tut tut The Economist. This is incorrect and naughty reporting. Whilst the CTA yes only applies to British and Irish Citizens, the CTA area, has become a "free movement zone" for CTA AND EU citizens. I'll explain.
The CTA is currently supported in legislation in all participating countries. The legislation that applies in UK law, is section 1(3) of the Immigration Act 1971 and the Immigration (Control of Entry through Republic of Ireland) Order 1972. These originally gave all Irish citizens exemption to any immigration controls. The right to simply walk in.
In 2014 Article 4 of the 1972 Immigration order was replaced by an exemption for EEA/ Swiss nationals and their family members (can I call them EU citizens for ease of typing?) who have a right under EU FOM .
Now that was the very very important bit, the Economist writer has disregarded. Let me be clear, under the Immigration (CoEtROI) Order 1972, Article 4, 2014 ammendment, all EU nationals can indeed enter the UK from the ROI without any immigration control (showing of passports etc) . They can just walk in.
All our other borders, airports, ferries, eurotunnel, etc do indeed enforce immigration control and passports and proof of EU citizenship at the point of entry, and why the ROI since 2014, have acted on our behalf controlling entry into ROI because from that point forward any EU national can just walk on through.
The legislation on the ROI side is under their Immigration Act 2004. Everyone who is not Irish or British is classed as a 'non-national'. Any non-national (and this is what applies to the current invisible border with NI) that arrives by land, must obtain immigration permission within 1 month of entry. EU nationals arriving by land must have their passports/valid ID, just as they would entering by air or sea. They may be asked to produce these. (There are currently numberplate recognition and cctv cameras on the Irish /NI border)
In the IOM (who is not a member of the EU) they accomodated the CTA to cover EU citizens by their Immigration (EEA) Regs 2009.
The channel Isles (trade only arrangement with the EU) accomodated the CTA amended their European Communities Law 1973 to accomodate EU citizens.
etc etc etc
From the EUs side, the 'CTA' was covered by Protocol 20 of the EU Treaty. Protocol 20 allows the UK and Republic of Ireland to ‘continue to make arrangements between themselves relating to the movement of persons between their territories (‘the Common Travel Area’)’.
(The EU have no juristriction over the IOM, Channel Isles etc hence not included in the EU Treaty)
In short, because of the difficulties of the CTA when the soft border was agreed, and the conflicting EU 'freedom of movement' rights, participating countries in the CTA extended the same rights of CTA entry to EU citizens, irrespective of whether that country was a member of the EU or not. There is no reason whatsoever, why EU citizens dont retain their rights to travel to the UK under the CTA friendly UK legislation. No reason whatsoever. The IOM, Channel Isles etc etc have already accomodated EU citizens within the CTA, theres absolutely no reason why the UK wont do the same.
They are and will always be welcome to visit the UK. Brexit is not a banning of europeans from visiting the Uk. Brexit is changing the terms of those visits.
Lets assume a 'hard' Brexit line. An EU citizen will not be able to stay for longer than say 3 months, they will not be able to live here (unless residency is applied for under normal immigration rules etc) and claim government support. They will not be able to work here. None of those things require a hard NI/ROI border as the ROI already control immigration at the point of entry (and keep out those naughty EU citizens who arent eligible to FOM. It works.
There is however, always the possibility of non-EU citizens inadvertantly breaching immigration rules by crossing the unmanned NI/ROI border. Heres what the NI Law Centre said about it.
" Callers to our advice line are often surprised to hear that, while the CTA is a “free movement zone” for CTA and EEA nationals, it is not so for other nationals. This lack of awareness can result in people committing an offence by crossing the land border. In some cases, this can lead to detention and removal. Clearly, this brings with it a high human cost as well as the economic cost of immigration enforcement. "
Current immigration control works.
Coming back to your article, there are 2 premises that the writer is stacking his 'high risk of hard border' argument on. Trade and people. Trade, hes basing it on TMs current stance of no customs union. That is absolutely not going to be the case as I explained why regards VAT earlier. Its not just me being an optimistic 'leaver' making up arguments as I go along, its the reality that a/ for both the UK and the EU, its free money and a lot of it, but b/ TMs stance is quite simply one of negotiation in that we do indeed have the right to stop VAT. In one fell swoop we can reduce our import costs from the EU by 20%. Thats a massive amount of money to negotiate with. Would you like your new Merc to cost 20% less overnight? Of course shes sticking to her guns at this stage.
The position over people, well they just wont discuss it yet. The EU have set the agenda and so be it.
These highly emotive articles are going to be rammed down our throats for the next 12 months. Its spin. Its fearmongering, and theyre utterly unfounded.