These could be imposed after the two years of mandated talks on a future relationship with the EU when the UK decides to trigger Article 50 under the Treaty on European Union (EU).
If Britain then refuses to allow free movement of EU workers into its economy, it could be barred from the European Economic Area (EEA) halfway house EU membership used by Norway and Iceland, which involves duty free trade in industrial goods.
The UK would then have to negotiate a bilateral free trade deal with the EU, but to secure comprehensive free trade, it may have to allow unrestricted immigration from remaining member states. And this is precisely the main reason why the Leave campaign prevailed on June 23, making it politically toxic for the British government.
If it failed to persuade the EU to allow full free trade alongside immigration controls on EU citizens, then standard duties...