Eitan Urkowitz: British Prime Minister Theresa May recently announced that the UK will consider allowing EU citizens concurrently residing in Britain to remain in the UK post Brexit. Joining me is Jacob Kirkegaard, Senior Fellow at the Institute. Thank you for joining me, Jacob.

Jacob Funk Kirkegaard: My pleasure.

Eitan Urkowitz: So why is Theresa May making this offer?

Jacob Funk Kirkegaard: Well, it's basically a direct function of the fact that the EU has told the UK that until we settle this and several other issues, we cannot continue into the parts of the Brexit negotiation that concerns the forward looking free trade agreement, which is what Theresa May actually wants to move on to. So she needs this issue first.

And that's what she has tried to do with this offer, because this is a very politically contentious issue. We're literally talking about millions of people's everyday lives.

Eitan Urkowitz: So is this a concession on her part? Or is this going to further complicate the negotiations?

Jacob Funk Kirkegaard: Well, she certainly tried to spin it as a major concession and magnanimous offer from the UK government to the more than 3 million EU citizens living in the UK, but I think that when the EU looks at this offer, they will say, "Well, wait a minute, we actually ourselves offered something."

Which in terms of the rights enjoyed by either EU citizens living in the UK, or British citizens living in the other EU countries, was actually more comprehensive than what Theresa May is offering."

So they may not necessarily view it as particularly generous. But there are also significant other issues here, because what the EU suggested several weeks ago is basically sort of a continuation of the status quo. Which means that all the rights that EU citizens hold today, being EU citizens in an EU country, also in the UK, would continue also after Brexit.

That's not just the right to stay, work or things like that, it's a lot of auxiliary rights, family reunions, basically the right to bring things like spouses from a third world country, a third country, et cetera into the UK. Things like that.

Eitan Urkowitz: So what are some of the other basic factors that EU citizens and British citizens, how will their basic lives be affected, for ones that are in the other region?

Jacob Funk Kirkegaard: Well, basically, a lot of sort of fundamental question here is, who is going to adjudicate these issues that really rely, relate -- it's very nitty gritty, it's very detail oriented family law, immigration law, details really matter. It's a matter of whether you get your loved one to live with you, whether you can stay in a country and things like that.

So details really matter. And therefore, a key, key issue will be what's the court? The EU has clearly said, "Look, we believe that these are EU rights. They are more expansive in many ways than rights enjoyed under UK law, and therefore, we want this to be overseen by the European Court of Justice. Fundamentally because we don't really trust the UK government and the UK court system to do so.

From the perspective of the UK, where Theresa May has clearly said one of the key reasons for Brexit is that she wants to end the jurisdiction of the European Court of Justice in the UK. That's a red line. And of course, she will also say that British courts are widely trusted and things like that.

So this is a big conceptual clash that will be very difficult to solve, in my opinion.

Eitan Urkowitz: And how many people could be affected by this measure?

Jacob Funk Kirkegaard: Well, I mean, so ballpark figures. You have 3 million EU residents or citizens residing right now in the UK and approximately just over 1 million UK citizens living in the rest of the EU, so well over 4 million people.

But then you have their dependents, you may have, let's say a British person living in Germany, but his or her children are living in the UK, but benefitting from child benefits and things like that. So the real number of people, EU citizens directly affected by this, whether from the UK or the rest of the EU, is certainly well above 4 million.

Again, this is a really big deal that you need to settle if you are going to have any chance of a successful Brexit negotiation.

Eitan Urkowitz:  Thank you, Jacob.

Jacob Funk Kirkegaard: My pleasure.