On Wednesday, President Donald Trump signed an executive order to end his policy on separating families at the border. But what will happen to the thousands of children who have already been separated from their parents?

Joining Boston Public Radio for his take on the immigration crisis — and what may happen next — was Gil Kerlikowske, head of Customs and Border Protection under President Obama. Kerlikowske is now a professor at Northeastern University.

A partial transcript of the interview follows.

MARGERY EAGAN: What does the executive order the president signed yesterday actually achieve?

GIL KERLIKOWSKE: I think it's unclear. There's been an analysis done. I think starting out by saying that 'It would really be up to Congress, that this is what the law demands, that no executive order can undo what's being done' — and then to sign an executive order that actuality undoes that, makes a bit of a mockery of all the discussion that has gone on from the White House in the past month on this. It does say families will be held together and under a current settlement which goes back actually to Janet Reno days in the Department of Justice [in] the 1990s called the Flores agreement, they can only be held for 20 days. I think the administration and the Department of Justice will be looking for some relief from that 20-day period.

JIM BRAUDE: I'm sure you have never heard what I'm about to broach, that it's all Obama's fault and it was not President Trump who started this policy of separating kids from their parents at the border, but was Barack Obama. Where does the truth lie there?

GK: The truth is there were separations at times, by Customs and Border Protection and by Immigration and Customs Enforcement. Those were when people were arrested and being charged. If you cross the border more than once and are charged, it becomes a felony and not the misdemeanor it is right now for a first-time offense. If you are involved in smuggling drugs or smuggling human beings and you have a child with you, you're going to be prosecuted and certainly that person cannot be held with their child. I'll tell you, those numbers were minuscule, tiny, compared to the number of people coming across the border who were actually separated.

JB: The whole issue of what happens to the 2,300 kids have already been separated from a parent or guardian, whoever they came to the border with, how difficult is that task? Does our government have the ability, assuming the desire is there, to have reunification happen in all these cases?

GK: You could reunite. I think the government and Customs and Border Protection would take people out of the mix very quickly, usually within 24 hours, and turn them over to ICE. Customs and Border Protection has a pretty narrow role, which is to apprehend people coming across the border illegally or to process people very quickly into another system if they were making a claim of "credible fear"or asylum. I would think that they could be reunited and I think it seems a little bit ridiculous that you wouldn't reunite them after signing an executive order, though I saw strong statements that this group would not be grandfathered in. That doesn't seem to make a lot of sense.

ME: Logistically how difficult is it? The numbers, as you point out, are not minuscule. They're significant. We have stories of children being shipped all the way across the country to New York City. How hard is it?

GK: Well, you know who the parents are and you know who the children are, and you could reunite them. I think one of the questions that will be talked about quite a bit is: Where are you going to have these spaces for these family units? I think that makes a great deal of difficulty. The other part is: These kids have already now been exposed to some fairly traumatic events.

I also, of course, worry about the border patrol agents who were tasked with separating the children. I've watched them deal with 68,000 unaccompanied children in the summer of 2014 and, quite frankly, I could not have been more proud or more impressed with the way they handled those kids — bringing t-shirts from their own kids at home, microwaving burritos, etc. Now, they've just been asked with separating kids with the last several months. I don't know how you do that and go home and look at your own kids. I get worried about them.