What I cannot fully understand is that neither side wants to give any guarantees in advance regarding the rights of EU citizens in the UK. or British people living in Europe. Merkel is adamant that there will be no informal negotiations before Article 50 is invoked, and May is determined not to show her hand in advance ok. I can understand that. But, there is a very good chance that the status of immigrants already resident - with residence permits (and migrants within the EU. have, de facto, unrestricted residence permits), would be protected by international law - firstly by the Vienna Convention and secondly by the UN. Can a permanent residence permit be legally taken away ? Can the law act in such a retrospect way ? The position in international law is being looked into at the moment, but there is no information coming out. It could be that acquired rights are already protected regardless of what Britain or the EU. negotiate.